California Allergy Season: Peak, Timing, and Symptoms

Written by Andrew Wood
Updated: April 21, 2023
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Allergy season in California can be a difficult time for many residents. Various types of allergens such as tree, grass, and weed pollens can cause many symptoms. This article explores the peak timing and symptoms of California’s allergy season. It also provides tips for managing and reducing symptoms. Whether you’re a Californian or just visiting, understanding allergy season can help make this time of year more bearable. And we’ve got your pets covered too; we’ve included tips on how to recognize and treat allergy symptoms in animals.

snow in California
California’s diverse landscape includes many different natural habitats that produce allergens throughout the year.

© Par

What Causes Allergies?

Allergies are a common condition where the immune system reacts to harmless substances, known as allergens. These can include pollen from trees, grasses, weeds, mold, dust mites, pet dander, and certain foods. An allergic reaction occurs when an individual’s immune system mistakes an allergen for a dangerous substance. Your body releases chemicals like histamine to combat it. This can result in symptoms like sneezing, itching, and rashes. In more severe cases, difficulty breathing and anaphylaxis, a dangerous condition, may result. The most effective method of avoiding allergic reactions is to avoid exposure to allergens. Using medications such as antihistamines can also help alleviate symptoms.

Allergies Over Time

Allergies can fluctuate in intensity and may be different for each person. Regular exposure to an allergen can cause an allergy to worsen. For instance, a person living in an area with high pollen levels may experience increasing allergy symptoms over time. In contrast, some people may find their allergies improve or disappear as they age. For example, some children outgrow their allergies to certain foods or pollens. Additionally, some individuals may develop a tolerance to certain allergens which results in milder symptoms over time. However, some allergies can persist throughout a person’s life and symptoms may vary in severity over time.

Allergies can sometimes create other medical complications. Sinus pressure, headaches, and facial pain may be a sign of sinusitis, an inflammation of the sinuses. People with asthma might start to have more severe symptoms and more frequent asthma attacks. An ear infection can result from fluid buildup in the ears. Skin problems like rashes, eczema, or hives might result from allergic reactions. People with especially great sensitivity to certain allergens can go into anaphylactic shock when exposed to them. This is a medical emergency in which breathing is restricted and blood pressure drops catastrophically. People susceptible to this level of reaction should always carry an epi-pen.

Woman with allergy symptoms
Left untreated, allergies can cause other medical complications, some of them potentially life-threatening.


When to Expect Allergy Season in California

California has a rugged landscape with a lot of different climate conditions. Each area has its own specific flora and fauna. The main allergens in California are tree, grass, and weed pollens, as well as mold and dust mites.

  • Tree pollen is most prevalent in the spring, with peak season usually occurring in March and April. Common allergens include oak, juniper, and pine.
  • Grass pollen is most prevalent in the summer, with peak season usually occurring in May and June. Common allergens include Bermuda grass, Johnson grass, and redtop grass.
  • Weed pollen is most prevalent in the fall, with peak season usually occurring in August and September. Common allergens include ragweed, sagebrush, and pigweed.
  • Mold is present throughout the year, but can be more prevalent in the fall and winter when the weather is cooler and more humid.
  • Dust mites are present year-round, but their allergens can be more prevalent in indoor environments.

The exact timing of peak allergy season in California can vary depending on weather conditions. People can be allergic to different allergens and have different symptoms.

Mountain climber on Mount Whitney
Outdoor activities during California allergy season are more fun when your allergy symptoms are under control.


How Does Pollen Count Affect Allergies?

Pollen count, a metric used to measure the amount of pollen in the air, is calculated as the number of pollen grains per cubic meter of air. This measurement can be accessed through local news, meteorological offices, and online pollen forecast websites, specifically during the allergy season. It can aid individuals with allergies in determining the severity of their symptoms on a given day. A high pollen count is considered to be over 120 grains/m3. The pollination period in the United States is most active during the springtime between March and May, while in southern regions it can begin as early as January and have multiple peaks throughout the year. Keep in mind that pollen counts can be affected by factors like weather, location, and measurement methods, and may not be entirely accurate. Additionally, pollen counts can vary day by day depending on factors such as wind, rain, and temperature.

Allergy Season
Following the daily pollen count on the news during allergy season can help you plan your activities.

©Chad Robertson Media/

Methods of Allergy Testing

Allergy testing is typically a combination of physical examination, medical history, and specific allergy tests.

One common type of allergy test is the skin prick test. During this test, a medical professional places a small amount of various allergens on the skin. They make a small prick through the allergen with a needle. If an individual is allergic to a specific allergen, they will develop a raised, red bump at the site of the prick.

Another type of test is the blood test, specifically the RAST (radioallergosorbent test) or ELISA (enzyme-linked immunosorbent assay). These tests measure the level of immunoglobulin E (IgE) antibodies, which the immune system produces in response to an allergen. A high level of IgE antibodies in the blood may indicate an allergy to a specific allergen.

A patch test determines contact allergens, which are substances that cause an allergic reaction when they come into contact with the skin. During this test, a medical professional places patches containing small amounts of various allergens on the skin for 48 hours. They observe the area for any signs of an allergic reaction.

Finally, a clinical evaluation by an allergist or immunologist can help to determine the type of allergy and suggest the best course of treatment based on the results of the tests and examination, as well as the patient’s symptoms and medical history.

These tests are not always conclusive and a positive test result does not necessarily mean that an individual has an allergy. In some cases, further testing or a food or medication challenge may be necessary to confirm the diagnosis.

Allergy Test
A skin test is a common way to find out what you might be allergic to.


Reasons You May Have Allergy Symptoms Without an Allergy

There are several reasons why a person who does not have an allergy may still experience allergy symptoms. A healthcare professional can help you determine if any of these are to blame:

  1. Non-allergic rhinitis: This causes allergy-like symptoms without a known allergen. Environmental irritants such as chemical cleaners or fragrances can cause it.
  2. Sinusitis: This is an inflammation of the sinuses that can result from allergies or from a viral or bacterial infection or from structural abnormalities in the sinuses.
  3. Psychological factors: Stress, anxiety, and depression can sometimes cause a runny nose, sneezing, and nasal congestion.
  4. Certain medications: Blood pressure medications, antidepressants, and some other medications can cause side effects that mimic allergy symptoms.
  5. Gastroesophageal reflux disease (GERD): Stomach acid can back up into the throat and nose, causing a sore throat, hoarseness, and postnasal drip.
A number of different conditions, such as stress or hormonal changes, may cause allergy-like symptoms even if you don’t have a specific allergy.


What Are Ways You Can Prevent Allergy Symptoms?

There are several ways to prevent allergies during the worst of California allergy season, some of which include:

  1. Avoiding allergens: The most effective way to prevent an allergic reaction is to avoid exposure to the allergens that cause it. This may include avoiding certain foods, staying indoors during high pollen counts, and using air filters in the home.
  2. Allergen-proofing the home: This can include using special air filters, keeping windows closed, and vacuuming frequently to reduce the number of allergens in the home.
  3. Immunotherapy: This is a medical treatment that involves exposing an individual to small amounts of an allergen over time in order to build up immunity to it. This can be done through allergy shots or sublingual immunotherapy (allergy drops or tablets).
  4. Medications: Antihistamines, decongestants, and nasal sprays can help to relieve the symptoms of allergies. It is important to consult with a healthcare professional to determine the best medication for your specific allergies.
  5. Maintaining a healthy immune system: Eating a healthy diet, getting regular exercise, and getting enough sleep can help to support a healthy immune system and reduce the risk of allergies.
  6. Keeping your environment clean: Regular cleaning of your home, office, car, and other areas where you spend a lot of time, can help reduce the number of allergens that you are exposed to.
dust mite
To prevent dust mite allergy symptoms, wash your bedding regularly in hot water.


Saving Money on Allergy Meds

Generic over-the-counter treatments can manage allergies just as effectively as their brand-name counterparts. Many brand-name allergy treatments have generic equivalents that are less expensive. Here are some links to generic alternatives of four well-known brand-name treatments, including the active ingredient in each product, so that you can make an informed decision about which treatment is best for you.

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 Allergies Can Your Pet Have?

Pets, like humans, can also suffer during allergy season in California. These are some of the most common culprits:

  • Flea allergies: Flea bites can provoke an allergic reaction. You might notice your pet scratching, biting, and licking at red, inflamed bites, sometimes leading to a secondary skin infection.
  • Food allergies: Itchy skin, diarrhea, or vomiting can be symptomatic of allergies to certain proteins or additives in pet foods.
  • Atopic allergies: Pollens, molds, and dust mites can cause your pet to sneeze, itch, and have red, irritated eyes.

Symptoms of pet allergies can overlap with other conditions such as infections and parasites, so you’ll need a proper diagnosis from a veterinarian. A veterinarian may conduct a physical examination, skin or blood test, or food trial to diagnose the allergy and recommend a treatment plan.

Cat licking its paws
Pets can have some of the same allergies as people. You might notice your pet biting, scratching, or licking themselves obsessively.

©Fayzulin Serg/

Are Human Allergy Medicines Safe for Pets?

Pets can take some human allergy medications, but it is important to consult with a veterinarian before giving any medication to a pet. Human medications can be harmful or even fatal to pets if not given in the proper dosage or if the pet has a pre-existing condition that contraindicates the use of the medication.

A veterinarian can recommend the appropriate dosage and the best form of medication for a pet, as well as monitor the pet’s response to the medication. Some common forms of allergy medication for pets include antihistamines, corticosteroids, and immunomodulators.

Appropriate medications also differ depending on the type of pet. Over-the-counter antihistamines such as diphenhydramine are safe for dogs in appropriate doses, but they can be toxic to cats. Similarly, some medications like decongestants are not recommended for pets.

Since pets can’t communicate their symptoms or side effects, owners must monitor them closely for any changes in behavior, appetite, or overall health, and immediately inform their vet if they notice anything unusual.

spay a dog at petsmart
Your vet can help you figure out for sure what your pet is allergic to and how best to treat it.


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Los Angeles, California, United States. City skyline view. Spring time cherry blossoms.
Los Angeles, California, United States. City skyline view. Spring time cherry blossoms.

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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!

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