House Dust Mites and Monsoon Season in Phoenix

It is monsoon season in Phoenix and the weather is hot and sticky.   As uncomfortable as it may feel, the outdoor humidity level in Phoenix this time of year rarely exceeds 50% and the indoor humidity levels in the typical Phoenix home, with air conditioning running day and night, may average no more than 30-40%.   These levels are still fairly low when compared with the dripping misery the residents of Houston, Mobile, or Chicago have to endure every summer, but significantly higher than the desiccating 21% average humidity in our winter and spring.

Average Humidity In Phoenix 2016

Humidity levels In Phoenix, AZ  July 2016

Humidity levels Houston, Texas August, 2016

Humidity levels Houston, Tx  August, 2016

Why is this important for people with allergies? Many migrants to Phoenix from more humid lands do say that they feel better  living in the dry, desert climate but most important from an allergy perspective, low humidity means no dust mites.

The House Dust Mite is the poster child for indoor allergies in many parts of the world. downloadInnumerable numbers of these microscopic insects eat, grow, raise families, and poop in the part of the home were we spend most of our time, the bedroom.   They like our beds because it provides a rich source of their favorite food: people dander. House Dust Mites feed on the dead skin scales (dander) than we leave behind while tossing and turning trying to get our 8-10 hours.   After a zillion generations of living, eating, pooping, and dying in our beds, the accumulation of house dust mite related “material” in our mattresses, pillows, and comfy down comforters can be disgustingly rich. And all of this is allergenic.
sleeping girl

House dust mite allergy is a major cause of allergic rhinitis and asthma and significant recourses have been directed at limiting our exposure to dust mite allergens in the home, including pillow and mattress covers, removing stuffed animals from the bedroom, pulling up carpeting and rugs, removing upholstered furniture, taking out venetian blinds, and (Say it ain’t so!) removing ceiling fans, to name a few. However in spite of all these disruptive and potentially expensive undertakings in the fight to control the lowly mite,  the most effective deterrent by far has been to reduce indoor humidity.

Like most living things, House Dust Mites are mostly water and since they cannot go downstairs to get a drink of water when they get thirsty, they need to absorb moisture from the atmosphere. Many studies have shown that indoor humidity levels of around 75% are needed for dust mites to thrive.

Which brings me back to why humidity in Phoenix is an important allergy topic. I recently started monitoring the humidity level in my home with a hydrometer. This device keeps track of the current, low, and maximum humidity levels in the home year round.


2017-07-18 09.05.17This is a picture of the hydrometer’s current reading. The indoor humidity has stayed around 30-40% during our most humid time of year with a rare spike to just above 50% during a recent storm.   These humidity levels are too low to support House Dust Mite growth.

Unseen monsters, particularly those as ugly as the House Dust Mite, are frequently blamed for our problems when the real cause is unknown, but when we are experiencing mystery allergy symptoms in the home, unless there is an indoor source of moisture, such as an evaporative cooler  or a 500 gallon indoor aquarium or hot tub, a home may contain a lot of dust but not dust mites. Steroid Devil

What Is In Allergy Shots?

A patient’s father recently asked me an insightful question about allergy immunotherapy. Allergy shots had been recommended for his son to treat his seasonal allergy and asthma symptoms and he wanted to know how we decided what allergens to include in the serum.

In some cases, as I explained, the answer is fairly straightforward. If his son had year round allergy symptoms that worsened when he was home on weekends, a very strong reaction to cat dander on allergy testing, and lived in a home with six cats, desensitizing to cat would definitely be a high priority.

More often, the decision is a little more involved but we start with the  following questions:
1. What is the patient sensitive to on allergy testing? When we read an allergy test, a positive reaction is defined as an increase in wheal size (raised area) of 3 mm or greater compared with a negative control or redness around the test site of 10 mm or greater. Skin test reactions are often much larger, however for an allergen to be considered clinically significant, it only has to reach the minimum size.

2. Is the patient currently exposed to the allergens that show positive on the allergy test?  The answer to this can be a bit tricky. For example, a number of people show positive reactions to House Dust Mite on allergy testing. And yet, most experts agree that House Dust Mite levels in the typical Arizona home are too low to cause significant symptoms. This is because House Dust Mites need an indoor humidity level of at least 50% for most of the year to thrive and the majority of homes in the Phoenix area rarely have indoor humidity levels this high. When there is a question, a simple test is to measure the indoor humidity levels in various rooms in the home with an inexpensive hydrometer. Unless the hydrometer readings are above 50%, we may not need to include Hose Dust Mite in the serum mix. However, if a patient frequently travels to more humid climates (anywhere but the South Western United States) and has increased symptoms on these trips, treatment for House Dust Mite may be recommended.

House Dust Mite

House Dust Mite

Why would you react to an allergen on an allergy test if you are not exposed to it?   There are several possible explanations. Your allergic sensitivities  may have developed when you were living in an area where the allergen is more prevalent. For example, if you lived in New Orleans for a number of yeas before moving to Arizona, you might have a strong sensitivity to House Dust Mite on an allergy test because of the high level of mite exposure on the Gulf Coast, but mites would be an unlikely cause of allergy problems in your new home in the desert. Cross reactivity is another reason that you may show a positive test to an allergen that you  have never been exposed to.   For example, the major allergenic protein in House Dust Mite is also found in a number of other insects and is also present in the muscles of  shellfish. If you are allergic to shellfish, you may show a positive reaction to House Dust Mite on testing, even though you have never lived in an area where dust mites are prevalent.

Cat and dog dander exposure is another issue. Several studies have shown that animal dander in school classrooms and work places may reach levels high enough to cause allergy symptoms in sensitized people, even if they do not have pets. It is also possible to bring enough dander home from school or work on your cloths for levels in your home to reach symptom-causing levels!

You can have pet dander without having a pet

You can have pet dander in your home without having a pet

3. Can the allergen be avoided or eliminated from the environment? If a patient has significant allergy problems caused by an indoor pet and that is the only thing they are allergic too, relocating the pet from the home might be the best solution.   This is certainly true in principle but relocating a family pet from the home is frequently not an option and so management with allergy injections may be the only long term solution.

4.  Is the allergen available for immunotherapy? If you developed allergy problems soon after bringing home a pet llama from your travels to Machu Picchu, appropriate material for desensitization may not be readily available.  Because of cost restraints, the companies that provide the material for making allergy immunotherapy extracts limit choices to items that are frequently used.  Even though Phoenix is the 5th largest city in the US, the percentage of people that are exposed to the unique allergens of the Sonoran Desert is small compared with other regions.  For this reason, some allergens that may be important for those living in our area may not be available. For example, Palo Verde, the state tree of Arizona, is not generally available for allergy immunotherapy. What goes into allergy shots 2

Goodbye Pecos Road: Our Lungs Will Miss You

For many years, residents of the shinny new master-planned communities of Mountain Park Ranch, The Foothills, and Club West in Ahwatukee had only one way in or out of their neighborhood, giving it the distinction of being called (not so fondly) the largest cul-de-sac in America. To get to work you had your choice of using either Chandler Blvd or Ray Road, two giant arms of a horse shoe-shaped loop, both with a million cars stopped at a million red lights, all trying to get to the interstate at the same time every morning and back to home and supper at the same time every evening.   This tedious, wearisome daily exercise in commuter angst was the one thing that made many homeowners seriously question the wisdom of moving to Ahwatukee.

Then Pecos Road opened up: Ten miles of four-lane heaven connecting the outer frontier of Ahwatukee to Interstate 10 with only three lights.   Like most residents of The Foothills or Clubwest, Pecos Road was my daily commute. I was greeted with hopeful sunrises over the East Valley each morning and contemplative sunsets over the Estrella Mountains and Gila River Indian Reservation in the evening.

pecos sign3I took up cycling 5 years ago (mid-life crisis or early onset dementia?) and like most of the local lycra-ed community trying their best to out-pedal old age, Pecos Road became my second home; the place for serious training when long intervals were needed or to join friends for group rides and the occasional kamikaze sprint at the roads end. On Pecos you could spread you wings and fly for miles.

In less than a year from now, all that will change and Pecos Road will be no more, replaced by a freeway that will provide a bypass route for an endless line of trucks plodding West or East on Interstate 10.

truck-1499377_1920 2


The passing of Pecos Road and the coming of the trucks was on my mind today when I read two articles in the Journal of Allergy, Asthma, and Immunology about the harmful effects of living close to a busy freeway.

The first: Inhalation of diesel exhaust and allergen alters human bronchial epithelium DNA methylation, presents evidence that exposure to diesel particles and common environmental allergens, such as pollen and mold, can alter the DNA of the lung.   This change can produce lasting effects on gene expression, cell function, and health. In other words, exposure to diesel particles can alter your DNA in such a way that you develop allergies or asthma, even if you, or your relatives, never had allergies before.

The number of people with allergies and asthma has increased significantly over the past several decades – a rise that has occurred almost exclusively in industrialized countries.   Since exposure to air pollution is one of the factors that characterizes life in the developed countries, the alteration of our DNA by diesel particles may be one of the mechanisms responsible for the world-wide asthma and allergy epidemic.

The second article, Traffic-related air pollution exposure is associated with allergic sensitization, asthma, and poor lung function in middle age, reports more bad news for communities planted close to major freeways.   Numerous studies have shown exposure to traffic-related air pollution to be associated with respiratory problems in children. This study, however, focused on the effect of air pollution on middle aged adults. The researchers concluded that even relatively low levels of air pollution during middle age is associated with increased risk of allergic sensitization, asthma, and diminished lung function.

The growing body of information documenting the harmful effects of traffic-related air pollution is certainly concerning to residents of any community located close to a major freeway. It doesn’t help that in Ahwatukee, these harmful health effects compound the growing sense of loss that many feel as they watch progress take away an old friend.

Brian Millhollon, MD




Why Do We Have Allergies 2: What Went Wrong?

We Are Not Alone

If you are looking for a trendy term to impress your friends or co-workers, try microbiome. The microbiome refers to the fascinating world of microorganisms (bacteria, viruses and fungi) that not only fill every nook and cranny of the planet we live on but also every nook and cranny of our own bodies.

By some estimates, we have as many microbes living in our bodies as we do our own cells. (Wouldn’t that be a cool fact to throw out at a dinner party?) For the most part, those microbes living in and on our bodies share a symbiotic relationship with us, meaning they help us and we help them. Supposedly, my dog and I share a symbiotic relationship: I provide him food and shelter and he, well… he hangs around the house looking cute and chewing up my shoes and socks.  (Come to think of it, this may be more indicative of a parasitic relationship.)

Not only do the microorganisms in our body help us digest our food, produce vitamins and help fight off infection, they play an important role in regulating our immune system. From infancy on, these single-celled animals communicate with our immune system and explain the ways of the world to it. It is believed that this early-life education is essential for our immune system to grow up and act appropriately: attacking bad guys – like the measles virus – and not reacting with good things like breakfast or the dander from the sock eating dog.

Of course, the process of this early-life microbial education can involve infection.  And yet, these are usually not life threatening infections, and the end result is a strong, wise and well behaved immune system.What Went Wrong- (1) 2

We No Longer Live in the Garden

Getting back to the question of what went wrong to cause us to have allergies, one of the theories is the hygiene hypothesis which proposes that our immune system is adapted to an environment that – at least for people living in Ahwatukee and most of the westernized world- no longer exists.   At one time in our history, our environment was much more complex and diverse from a microbial point of view with exposure to farm animals and other elements of a farming environment as well as large families with lots of runny-nosed siblings to play with. The hygiene hypothesis was proposed in 1989 when researchers noticed that children who grew up on farms or who came from large families with lots of siblings had fewer allergies.

Untitled design (59)

The explanation? Progress and myriad changes associated with modern life such as a decrease in natural birth deliveries, antibiotic use, lack of breast-feeding, pasteurization, Lysol in every kitchen and bathroom, and antimicrobial everything (hand wipes, mouth wash, soaps, detergents) – not to mention a noticeable lack of cows, chickens, and pigs in the yard -reduce an infant’s exposure to the wise microbe masters that once kept or immune system from going down the path of the dark side.Untitled design (58)

Just as children who grow up in an overly protective, sterile, and restrictive parental environment may have difficulty coping with challenges later in life, our pampered undirected immune system may react inappropriately.

The unintended consequence of our quest to control everything has been the emergence of allergy and other chronic inflammatory diseases.  Who knew?

Now that we are beginning to understand why we develop allergies, the big question is how to fix it.  Allergy immunotherapy or desensitization is essentially a way of re-educating the immune system to behave more appropriately towards our environment.   It is not a quick fix, but the end result can be life-long immunity to things we are allergic to.  New forms of immunotherapy are in the works that combine conventional immunotherapy with elements of the microbiome to mimic the type of early-life training that has been lost (along with paradise).

Brian Millhollon, MD


Ahwatukee Oak Alley

I attended medical school in New Orleans.  Along with great food, music and the rich culture and history, one of my fondest memories was the magnificent Southern Oak trees.

These ancient giants, some dating back to the Civil War, with trunks the size of a Volkswagen beetle, hanging with moss, framed an idyllic image of the old south.  They are beautiful trees but they are also one of the major causes of spring allergy problems throughout the south.

When I moved to Arizona and started an allergy practice, I was sure of one thing:  I would not have to worry about Southern Oak allergy problems in Phoenix!

I was wrong.

I have known that there are several varieties of Oaks native to Arizona, the majority of which live at higher elevation in the state, and rarely in Phoenix.  But certainly, there were no trees resembling the Oaks I knew from the south, growing in a typical, low water use, desert landscaped yard in Ahwatukee!

Souther Oak Trees Lining Lakewood Drive in Ahwatukee

Oak Tree Pollen

And yet, if you take a drive around the lakes of Lakewood, in Ahwatukee, (as I did on my bike a few weeks ago), you will find the entire seven mile stretch lined with mature Southern Oak trees.  No hanging moss or women in antebellum dresses swinging on porch swings, but most definitely full of pollen.

If You Are Sneezing in Ahwatukee and It’s February – It’s the Ash Trees!

I was visiting a friend last week who lives next to Altadena Middle School. He has two very large, stately trees in his back yard that provide great shade during the summer. In February however, there are no leaves on the trees. Just packets of pollen clusters. The branches are heavy with them.

Ash Flower

Ash Tree Flower








These Ash trees also line the sports fields of Altadena. And once you start to look for them, they are everywhere: in local parks, schools, green belts, and your neighbors yard. All heavy with the same pollen sacks. I took a few pictures while riding my bike and found a large number of Ash trees in Vista Canyon Park next to Desert Vista High School.

Flowering Ash Trees, Vista Park, Ahwatukee, Phoenix

Flowering Ash Trees, Vista Park, Ahwatukee, Phoenix








Interestingly, the logo for the Phoenix Parks and Preserves Initiative is an Ash leaf !

Ash Leaf Logo

Phoenix Parks and Preserves Ash Leaf Logo








More than half a century ago, tree pollen counts in Phoenix skyrocketed. The culprit, the popular Olive tree. From an allergy standpoint the Olive tree is a monster. March through May, Olive pollen fills the air and is incredibly sensitizing with many new residents becoming allergic after just one season of exposure.

So notorious is the Olive for causing allergy problems that it has been banned in a number of cities including Tempe and Phoenix and so you will not see many in the newer communities in Ahwatukee. Unfortunately, the Olive happens to have a close allergy cousin, the Ash tree. Most people who react to Olive on allergy testing will also react to Ash, a form or cross-reactivity. Some allergy-control progress may have been made in limiting Olive tree planting, but this progress has likely been lost in the rising popularity of the Ash tree.

Arizona Air Quality: Ozone and Outdoor Exercise

I am discussing air quality in Arizona, particularly as it affects patients with allergies and asthma. Previously, one of the most important pollutants, Ozone was discussed and in this post I will continue with some of the special problems associated with ozone exposure and outdoor exercise.

For a number of reasons, athletes are particularly vulnerable to the adverse effects of air pollution.  A distance runner training for a marathon or a cyclist getting ready for a century ride, will spend hours every day inhaling huge volumes of air during the course of a workout. In fact, a cyclist may inhale 80 liters of air a minute for an hour during a race.


Cyclists on South Mountain. Notice haze sitting over Ahwatukee

Exercise not only increases the volume of air that we breathe, but the high velocity of air movement sends particles deeper into the lungs.  Blood supply to the lung in also increased to absorb more oxygen, which will also allow greater absorption of any contaminants found in the air. In addition, many athletes breath through there mouth when exercising, bypassing the filtering effect of the nose.

The end result is that during exercise, the tissues of the nose, sinuses, airways, and lungs endure intense exposure to particulate and vapor pollutants such as ozone.  Obviously the greatest risk of exposure to ozone is likely to occur when exercising in the city close to traffic, particularly in the summer when the sun is shining, but because ozone can travel great distances, you cannot escape it’s effect if you live and exercise in a more rural part of Arizona, such as Ahwatukee or Cave Creak.

Because of the increased exposure to the oxidizing effects of ground level ozone with exercise, the cells lining the respiratory track can be injured. In fact, studies have shown that exposure to ozone can cause the lining of the airways to become “leaky” allowing other particles in the air such as pollen and mold spores to have greater access to our immune system, aggravating and even possible causing, allergies and asthma.  Many studies have shown that children living close to automobile traffic have increased lung problems including asthma.

Long distance runners have been found to have reduced mucocilliary function in the nose. The mucocilliary system helps to clear toxins and debris from the respiratory system and is important in our defense against infection, so a weakness in this system increases the potential for further injury and damage to the airways from air pollution.

Exposure to ozone can cause a variety of immediate symptoms including nasal and throat irritation, coughing, wheezing, shortness of breath, and pain with deep inspiration.  In addition, a measurable decrease in lung function and exercise performance can occur which worsens the longer you exercise.    Ozone exposure can cause inflammation in the airways resulting in painful breathing.  This combination of reduced lung function and painful breathing can significantly limit an athlete’s ability to perform.

Interestingly, the respiratory symptoms associated with ozone exposure mimic exercise induced bronchospasm.  Unlike EIB however, ozone related symptoms do not improve with asthma medications such as albuterol.  In some cases, ibuprofen and other non-steroidal anti-inflammatory agents have been helpful in reducing the pain, coughing, and breathing limitation associated with ozone induced inflammation.

Air Quality in Arizona: Ozone

I will continue the discussion on air quality in Arizona, particularly as it affects patients with allergies and asthma, beginning with one of our most important pollutants: ozone.

diagram-29982_1280 (1)Ozone in the upper atmosphere is our friend.   This thin layer of gas floating between 6 and 31 miles above the earth’s surface protects life on our planet by filtering harmful ultra violet rays from the sun.

Ground level ozone is another story.  This insidious byproduct of automobile exhaust can damage living tissue just as it’s relative in the upper atmosphere protects it. Even the chemical structure of ozone looks like it would be friendly enough: it is just like oxygen, O2, with one more oxygen atom added to make O3 -a super oxygen!

But as vital as oxygen is to sustain human life, too much can be deadly.  To understand why, think about the effect of oxygen on a forest fire on a windy day or what happens to an unpainted iron fence -even in Arizona where it rarely rains.

Rusty BoatWhen wood burns or iron rusts, oxygen is at work in a process called oxidation. Oxidation can turn a battle ship into a heap of rust and kill all the bacteria and algae in your swimming pool.

In fact our immune system uses the deadly effects of oxidation to fight off disease.  Our white blood cells release powerful oxidizing chemicals like hydrogen peroxide and what are called, “reactive oxygen species,” or ROS, that kill and even digest invading pathogens.  This is great when you need to get rid of an infection, but we don’t want these chemicals loose in our bodies digesting us.090114_2215

To keep our white blood cells from eating holes in our lungs and liver, anti-oxidants are produced that are capable of neutralizing the oxidizers and preventing damage. Important antioxidants include vitamin A, vitamin E, beta-carotene, vitamin C, and glutathione as well as many other compounds found in food, especially vegetables and fruits.

When chronic inflammation occurs as a result of injury, infection, allergies, or immunologic processes, excessive amounts of these oxidizing chemicals are produced creating a condition called “oxidative stress”.  This stress can contribute to the pathogenesis of a wide variety of disease states including heart failure, atherosclerosis, and cancer as well as to the normal process of aging.

The role of diet and vitamin supplementation in the treatment and prevention of chronic disease is an important subject and one that I will review in more detail in a later post.   For now, the point I would like to make is that oxidative exposure from external sources can overwhelm our anti-oxidant resources and can contribute to the development and exacerbation of chronic disease.

Which brings us back to ozone.

Ozone is a killer oxidizing agent – powerful enough to be used commercially to sterilize water supplies. It is definitely not something you want to spend much time inhaling.  Exposure above as little as 100 ppb (parts per billion) can be harmful, causing symptoms such as nose, eye, and throat irritation, coughing, wheezing, shortness of breath, painful breathing, nausea and headache, and has been linked to increased incidence of asthma, bronchitis and heart disease.  Long-term exposure has been linked to increased risk of death from lung disease.

Untitled design (36) (1)According to the Maricopa Air Quality Department, ozone levels in our area are can reach unhealthy levels on “hot, sunny days when there is little wind”, which pretty much describes most days in Phoenix from May until October. For example, about a week out of the month of July, 2013 were under a high pollution advisory and health watch for ozone. This year the American Lung Association ranked Phoenix as the 11th most polluted city in the US for ozone.

In recognition of the adverse health effects of ozone, air quality guidelines have been established by the World Health Organization, European Union, and the US Environmental Protection Agency (EPA).   In 2010, the EPA announced proposed revisions to the National Ambient Air Quality Standard (NAAQS) for ozone with the following statement:

EPA proposes that the level of the 8-hour primary standard, which was set at 0.075 μmol/mol in the 2008 final rule, should instead be set at a lower level within the range of 0.060 to 0.070 μmol/mol, to provide increased protection for children and other ‘‘at risk’’ populations against an array of ozone – related adverse health effects that range from decreased lung function and increased respiratory symptoms to serious indicators of respiratory morbidity including emergency department visits and hospital admissions for respiratory causes, and possibly cardiovascular-related morbidity as well as total non- accidental and cardiopulmonary mortality…

In addition, the Air Quality Index (AQI) was developed by the EPA to explain air pollution levels to the public. Using this scale, eight-hour average ozone levels of 85 to 104 nmol/mol are considered “unhealthy for sensitive groups,” 105 nmol/mol to 124 nmol/mol as “unhealthy,” and 125 nmol/mol to 404 nmol/mol as “very unhealthy.. The current AQI for Maricopa county and surrounding areas can be found at

Ozone exposure can have a significant negative impact on lung function, particularly in athletes involved in outdoor sports, a topic I will explore further in the next post.

Arizona Air: The Good the Bad and the Ugly

Phoenix is a wonderful place to live if you enjoy spending time out of doors.  However, there is a catch. The conditions that make for our predictable-practically-perfect weather (at least in the winter and spring) has also led to some serious air quality issues.

Every year the Arizona Department of Environmental Quality releases a number of high pollution advisories warning Arizonans that it may be unhealthy to venture out of doors, particularly if you have a medical condition such as asthma.  July and August show the highest number of “very unhealthy days”.  In fact in July 2013, there were seven “very unhealthy days” reported.

Over the next few posts, I will review some of the unique conditions that make up our Arizona environment and spend some time on the major components that make up the “poor air quality” reported by the Arizona Department of Environmental Quality

To begin, one thing is obvious: Phoenix is a desert.  Like most deserts, our climate is characterized by high pressure conditions that camps out over the region for extended periods of time resulting in warm (and hot!), dry, and generally clear conditions.   Half of the yearly rainfall occurs during the winter when brief pacific storms move through the region.   During the monsoon season, from July to September, moister from the south brings higher humidity and most of the remaining rainfall, often in the form of violent thunderstorms.

During late fall to early summer, high pressure sits over the region like a glass lid, repelling the volatile weather fronts that plaque much of the United States and keeping the interior toasty warm and dry.  What little wind does occur is generated by local temperature and elevation variations.  This, along with the extremely low humidity during this time of year, allows airborne particles -dust, pollutants, pollen-to drift in the atmosphere for a very long time rather than being cleaned away by rain or ocean breezes.

Conditions change somewhat during the second half of the summer when high pressure travels north a bit allowing monsoon moisture to move into the valley.  The increased volatility in the local wind patterns not only produces thunderstorms (and the hope of rain) but also massive dust storms.  These giant walls of dust can transport appreciable quantities of organic as well as inorganic material as they move across the valley.  Exposure to these clouds of organic bits of plants, mold and who-knows-what-else (think Maricopa feed lots) can trigger severe allergy and asthma attacks.  An analysis of material from dust storms in Tempe showed they contain an average of 11% organic material.

Although monsoon storms have the potential to bring rain and some clearing of the air, summer is the time when ozone becomes a problem. That will be the topic of my next post.

“My Worst Allergy Spring Was the Winter I Just Spent in Arizona”: Part Two

Arizona Ash Flower

While walking my dog several weeks ago, I noticed something unexpected; a number of ash trees in full bloom.   This was unexpected because it was the first week of February and ash trees usually pollinate later in the month.  It was also unexpected because this was near a school in the Foothills of Ahwatukee were the ash trees are supposed to be of a less allergenic variety.   This is in distinction from the Arizona Ash, Fraxinus velutina, which is notorious for it’s prolific production of allergenic pollen. For this reason landscapers have been discouraged from planting Arizona Ash trees for a number of years although they are very numerous in older communities such as the Warner Ranch area as well as old Ahwatukee and Tempe.

Ash trees are in the same family as olive trees, possible the most allergenic tree in Phoenix, and so people who are allergic to one will be allergic to the other

So the ash trees are pollinating a full two to three week early this year, probable because of the warm weather.  This along with large amount of Arizona Cypress and Juniper pollen in the air is creating a very difficult winter for people with allergies.