Seasonal allergies are diagnosed through skin prick testing, blood testing, or sometimes both. The skin prick test is the most common starting point because it’s fast, checks for dozens of allergens at once, and produces results in about 20 minutes. Your doctor will choose the right method based on your symptoms, medications, and medical history.
Skin Prick Testing
A skin prick test can screen for up to 50 different allergens in a single visit. In adults, it’s typically performed on the forearm; in children, the upper back is sometimes used instead. A nurse or technician cleans the skin with alcohol, draws small marks to label each spot, and places a drop of allergen extract next to each mark. A tiny lancet is then used to prick each drop into the skin’s surface, with a fresh lancet for every allergen. The lancets barely break the skin, so there’s no bleeding and only brief, mild discomfort.
Two control substances are always included. Histamine serves as the positive control (your skin should react to it), and saline serves as the negative control (your skin should not react). These confirm that the test is working properly. After 15 to 20 minutes, the test area is examined. A raised bump, called a wheal, with a mean diameter of 3 mm or more is considered a positive result. The larger the wheal, the more likely the allergy is clinically relevant, though size alone doesn’t predict how severe your real-world symptoms will be.
For grass and dust mite allergens, roughly 87 to 89% of positive skin test results match up with symptoms people actually experience when exposed. For other allergens, that correlation can be lower, around 40%. So a positive result doesn’t automatically mean that allergen is causing your worst symptoms, which is why your allergist interprets the results alongside your symptom history.
What a Standard Panel Covers
A typical seasonal allergy panel tests for the major pollen types that peak at different times of year. Tree pollen (oak, elm, maple) tends to peak from February through April. Grass pollen (Timothy grass is a common test species) runs from May through July. Weed pollen, especially ragweed, dominates from August into early October. Outdoor mold spores like Alternaria and Cladosporium typically spike in May through June and again in September through October.
Most panels also include year-round (perennial) allergens like dust mites, cat and dog dander, cockroach, and indoor molds such as Aspergillus and Penicillium. Testing for these helps distinguish seasonal triggers from ones that bother you all year, since the symptoms can overlap.
Blood Testing for Allergies
A blood test measures immunoglobulin E (IgE), the antibody your immune system produces in response to allergens. There are two types: a total IgE test, which measures your overall IgE level, and a specific IgE test, which measures how much IgE your body produces against one particular allergen. If your doctor wants to check for multiple triggers, separate specific IgE tests are run for each one.
A high specific IgE result suggests you’re likely allergic to that substance, but the number doesn’t predict how severe your reactions will be. Blood tests are particularly useful when skin testing isn’t an option. You might be directed to blood testing if you take medications that can’t be paused, have a skin condition like severe eczema covering the test area, or have a history of serious allergic reactions that make skin testing riskier. Blood allergy tests can be slightly less accurate in children under 5, though providers still use them when symptoms warrant investigation.
Intradermal Testing
If a skin prick test comes back negative but your symptoms strongly suggest an allergy, your doctor may follow up with an intradermal test. Instead of pricking the surface, a small amount of allergen extract is injected directly into the outer layer of skin using a fine needle. This method is more sensitive than the prick test, meaning it can pick up reactions that a surface prick missed. It’s commonly used as a second step for suspected insect venom allergies and medication allergies, and occasionally for environmental allergens when initial results are inconclusive.
How to Prepare for Testing
Antihistamines are the biggest concern before allergy skin testing because they suppress the immune response the test relies on. You’ll need to stop taking common antihistamines like cetirizine (Zyrtec), loratadine (Claritin), and fexofenadine (Allegra) at least 7 days before your appointment. The same 7-day rule applies to over-the-counter options like diphenhydramine (Benadryl), combination cold and sinus medications, sleep aids containing antihistamines, and nasal antihistamine sprays.
Heartburn medications like famotidine (Pepcid) contain a different type of antihistamine and should be stopped at least 1 day before testing. Tricyclic antidepressants also need to be paused a week ahead, but only with your prescribing doctor’s approval. Blood tests don’t require stopping any medications, which is one reason they’re sometimes preferred.
Why At-Home Kits Fall Short
Home allergy test kits are widely marketed, but most have a fundamental problem: they measure the wrong antibody. Instead of testing for IgE, which actually drives allergic reactions, many kits measure immunoglobulin G (IgG). IgG levels rise in response to foods and substances you’re regularly exposed to, not necessarily ones you’re allergic to. The American College of Allergy, Asthma and Immunology has cautioned that these results are difficult to interpret correctly and can lead people to unnecessarily restrict their diets or avoid harmless substances.
A positive IgG result on a home kit doesn’t mean you have an allergy, and acting on it without professional guidance can cause more problems than it solves. If you want reliable answers, skin testing or specific IgE blood testing through an allergist’s office remains the standard.
Testing Children for Seasonal Allergies
Skin prick testing is generally not performed on infants under 6 months old. For children under 5, blood tests can be slightly less accurate, but providers still recommend testing when symptoms are persistent or disruptive. Seasonal allergies are less common in very young children simply because it often takes two or more pollen seasons of exposure before the immune system develops a measurable response. Most children with seasonal allergies start showing clear symptoms between ages 3 and 5, though some develop them later.
The decision to test is driven by your child’s symptoms rather than a strict age cutoff. If your child has recurring sneezing, congestion, or itchy eyes that follow a seasonal pattern, testing can identify specific triggers and guide treatment choices.
What Happens After Testing
Once your results are in, your allergist maps your positive reactions against your symptom timeline. If you test positive for tree pollen and your worst months are March and April, that lines up. If you also react to dust mites, that could explain why symptoms linger into winter when pollen counts are zero. This layered picture helps shape a targeted plan, whether that means timed use of nasal sprays, specific avoidance strategies, or immunotherapy (allergy shots or sublingual tablets) for your dominant triggers.
Skin prick testing carries a very low risk of systemic reactions. In one large study, serious reactions occurred in about 0.16% of patients, and anaphylaxis in roughly 0.05%. This is why testing is done in a medical setting with monitoring, not because reactions are likely, but so they can be handled immediately if they occur. Most people walk out with nothing more than a few itchy bumps that fade within a couple of hours, though some experience mild redness and swelling at the test sites for a day or two.