Colorado Allergy Season: Peak, Timing, and Symptoms

Written by Andrew Wood
Updated: April 21, 2023
© Adventure_Images/
Share this post on:

With its beautiful mountains and diverse landscapes, Colorado is a popular destination for outdoor enthusiasts. However, for many residents and visitors, the changing of the seasons also brings on allergy season. Allergies can be caused by tree and grass pollen, or dust mites and mold. Colorado’s allergy season can cause symptoms such as sneezing, runny nose, and itchy red eyes. Here, we explore the peak timing and symptoms of Colorado’s allergy season. We also provide tips for managing and reducing the effects of allergens. We’ll also help you recognize allergy symptoms in your pet and consider what medication is appropriate. Whether you’re a long-time Coloradan or just visiting, understanding allergy season can help make this time of year more bearable.

Exploring Colorado is far more enjoyable when you have your allergy symptoms under control.


Allergies: What Are They?

An allergy is a condition where a person’s immune system reacts to an allergen. These can include pollen, mold, pet dander, and certain foods. The body tries to fight allergens by releasing a chemical called histamine, which causes symptoms. In really severe cases, anaphylaxis can create respiratory problems and a sudden lowering of blood pressure, which can be fatal. Allergies can change over time. For example, a person allergic to pollens during childhood may not be allergic to the same pollens in adulthood. Similarly, some people may develop new allergies as they get older.

44,379 People Couldn't Ace This Quiz

Think You Can?

It’s important for people with allergies to work with a healthcare professional to develop a plan. This will help manage their symptoms and reduce their exposure to allergens. This can include taking medications, making lifestyle changes, or undergoing allergy shots (immunotherapy). Shots help build up a tolerance to allergens over time.

Woman with allergy symptoms
Allergies happen when the body tries to fight off allergens like pollen, pet dander, certain foods, and others.


When is Peak Allergy Season in Colorado?

Colorado has a diverse climate that ranges from semi-arid in the eastern part to alpine in the mountains. Some of the trees in the western part of the states are aspen, Douglas fir, and Ponderosa pine. Wildflowers, mosses and lichens are found in the mountains. In the east, various prairie grasses such as buffalo grass and blue grama as well as sagebrush can aggravate allergies. The main allergens in Colorado are:

  1. Trees: Tree pollen is worst in the spring, typically from April to June, with pine, juniper, and aspen being some of the most prevalent tree allergens in Colorado.
  2. Grasses: Grass pollen is highest in the spring and early summer, typically from May to July, with species such as Bermuda grass, bluegrass, and timothy grass being common allergens.
  3. Weeds: The most common weeds that cause allergies in Colorado include ragweed, sagebrush, and Russian thistle. They are worst in late summer and early fall, typically from August to October.
  4. Mold: Mold spores are present year-round, but are worst in the warm and humid summer months, typically from June to September.

Considering that the severity of allergy season can vary from year to year and from place to place depending on weather conditions, it’s always a good idea to keep an eye on local pollen and mold count reports. Additionally, people can be allergic to different types of allergens, so what might be a big problem for one person may not be for another.

Colorado’s wildflowers are beautiful, but they make life difficult for some allergy sufferers.

©Sean Xu/

What is Pollen Count?

Pollen is a powdery substance released by plants during their reproductive process. Pollen count measures the concentration of pollen grains in a specific volume of air. A high pollen count means that the risk of an allergic reaction is greater. The level of what is considered a high pollen count can vary depending on the type of pollen and the sensitivity of the individual, but generally, a count of over 120 pollen grains per cubic meter of air is considered high.

During allergy season, local news channels and dedicated aps and websites report the pollen count daily. You may also find an allergy forecast that predicts the pollen levels for the next few days so you can plan your activities accordingly.

If the pollen count is high and you suffer from allergies, some things you can do are: staying indoors, closing windows and using air conditioning, wearing a mask when you go outside, avoiding outdoor activities in the early morning when pollen counts are highest, and showering and changing clothes after spending time outside. You can also take over-the-counter or prescription medication to relieve symptoms.

Allergy Season
On high pollen days, you can literally see the pollen on outdoor surfaces.

©Chad Robertson Media/

What is Involved in Allergy Testing?

Here are some of the ways an allergist can help you find out what you are allergic to:

  1. Skin Prick Test: The doctor places a small amount of an allergen on the skin, usually on the arm or back, and then pricks the skin. If the individual is allergic, they will develop a red, raised bump or wheal at the site of the allergen.
  2. Intradermal Test: The medical specialist injects a small amount of allergen into the skin, usually in the arm. This test is usually for people who have negative results in the skin prick test.
  3. Blood Test: A sample of blood is taken and then tested for the presence of specific allergy-related antibodies. This test can help identify allergies to substances that are not easily tested with skin or intradermal testing, such as certain food allergies or environmental allergies.
  4. Patch Test: A patch containing small amounts of an allergen is placed on the skin, usually on the back, and left in place for 48 hours. This test is used to diagnose contact dermatitis, a skin condition caused by an allergic reaction to certain substances that come into contact with the skin.
Allergy Test
A skin prick test involves putting allergens on the skin to see what causes a reaction.


Allergy Symptoms Without Allergies

Sometimes people have allergy symptoms even though allergy testing does not indicate they are allergic to anything. This is called non-allergenic rhinitis, which basically means you have allergy symptoms for unknown causes. Fortunately, it usually responds well to the same kinds of allergy medications as known allergies do.

Non-allergenic rhinitis creates allergy symptoms from unknown causes, but often responds well to allergy medication.


Preventing Allergies During Allergy Season in Colorado

One of the best ways to prevent allergies when you know what you are allergic to and when is the peak allergy season in Colorado is to avoid allergens. For example, on high pollen days, you might stay indoors, keep windows closed, and shower and change clothes after going outside. You can vacuum and dust regularly, wash bedding in hot water, use air purifiers, and keep pets restricted from certain areas of the house, such as the bedroom.

It’s also important to keep track of your symptoms and to seek medical attention if they become severe or if they interfere with your daily activities. Because allergies can change over time and new ones can emerge, keeping track of your symptoms and comparing them with the peak pollen season of various allergens can give you a clue as to what is bothering you. If a particular plant species is particularly problematic for you, you might find it helpful to alter the landscaping of your property, such as removing a tree or replacing a type of grass. Wearing a mask is another way some people reduce their exposure to large grains of pollen in the air.

dust mite
Dust mites create allergic reactions in some people. You can combat them by washing bedding in hot water.


Best Over-The-Counter Allergy Treatments

When it comes to dealing with allergies, it’s important to look at all your options, including generic medications. Over-the-counter medicines often have identical ingredients to brand-name options at a considerably lower price. Below are links to generic versions of some popular allergy medicines, showing you the main ingredient in each medicine, so you can make an informed choice.

Amazon Basic Care Loratadine Antihistamine
  • Long-lasting relief from allergy symptoms
  • Non-drowsy formula
  • Active ingredient is the antihistamine Loratadine (10 mg)
  • 24-hour allergy relief
Check Amazon
ValuMeds 24-Hour Allergy Medicine
  • 24-hour allergy relief
  • Works for pollen, hay fever, dry eyes, itchy eyes
  • Main ingredient is Cetirizine HCl
Check Amazon
ValuMeds Antihistamine, Diphenhydramine HCl 25 mg
  • 600 tablets
  • Active ingredient: Diphenhydramine HCl 25 mg
  • Suitable for Children and Adults
  • Relieves Itchy Eyes, Runny Nose, Sneezing

Check Amazon
HealthCareAisle Allergy Relief - Fexofenadine Hydrochloride
  • Active ingredient: Fexofenadine Hydrochloride
  • 90 tablets of 180 mg
  • Non-Drowsy
  • 24-Hour Allergy Relief

Check Amazon

What if Your Pet Has Allergies?

Pets can also have allergies. However, the frequency and severity of allergies can vary among different species and breeds. Even pets that may not have a history of allergies can still develop them at any point in their life. Pets can have allergies to a variety of things, including food, flea bites, pollen, mold, and dust mites. Symptoms of allergies in pets can include itching, scratching, biting or licking at the skin, red or irritated skin, and ear infections. In severe cases, pets may also experience hair loss, respiratory problems, and vomiting or diarrhea.

Treatment options for allergies in pets will depend on the specific cause of the allergy. For example, if a veterinarian suspects a food allergy, he may recommend a food trial using a hypoallergenic diet. If he suspects a flea allergy, he may prescribe spot-on treatments, sprays, or oral medications. For environmental allergies, such as pollen or mold, he may recommend antihistamines, steroids, or immunotherapy (allergy shots). If you notice any symptoms of allergies in your pet, it is important to see a veterinarian for an accurate diagnosis and appropriate treatment. They will help you to understand the best course of action.

Cat licking its paws
Licking, scratching, or biting at the skin can be signs of an allergic reaction in your dog or cat.

©Fayzulin Serg/

Can Pets Take Human Allergy Medicine?

Pets can take some allergy medications, but not all. Do not give pets human allergy medications without consulting with a veterinarian first. Many human allergy medications are not safe for pets and can cause serious side effects. Additionally, the dosage and administration of these medications may differ for pets, and many human allergy medications can interact with any other medications your pet may be taking. It’s always best to consult with your veterinarian before giving any medications to your pet, as they will be able to recommend the best course of treatment for your pet’s specific condition.

spay a dog at petsmart
A veterinarian can advise you on the best medications and correct dosage to help your pet be more comfortable during allergy season.


Up Next:

More from A-Z Animals

The Featured Image

Horse, Animals In The Wild, Colorado, Mustang - Wild Horse, Leadership
© Adventure_Images/

Share this post on:
About the Author

I'm a freelance writer, world traveler, and lifelong animal lover. Currently, I'm an "Emotional Support Human" to 4 dogs, 1 cat, and 2 guinea pigs. My favorite wild animal is the quokka, the most selfie-friendly animal in the world!

FAQs (Frequently Asked Questions) 

When is peak allergy season in Colorado?

Peak allergy season in Colorado depends on the source of the allergen. Tree pollen is worst in the spring, typically from April to June. Grass pollen is highest in the spring and early summer, typically from May to July. Weed pollen is at its worst in late summer and early fall, typically from August to October. Mold spores are present year-round, but are worst in the warm and humid summer months, typically from June to September.

Can pets take human over-the-counter allergy meds?

Pets can take some human allergy medications but it is essential to consult your veterinarian to decide upon the right medication and the dosage. Some medicines that work for dogs may be toxic for cats.

How are people tested for allergies?

You can be tested for allergies by seeing an allergist, who will do a skin test by putting small amounts of allergens on your skin to check for a reaction. If a red welt rises up, it means you are allergic to that substance. It is also possible to do a blood test to see if your body is producing antibodies against allergens.

Thank you for reading! Have some feedback for us? Contact the AZ Animals editorial team.