Allergists test for a wide range of triggers, from foods and pollens to metals, insect venoms, and medications. The specific panel depends on your symptoms, but most visits involve testing for environmental allergens (like dust mites, mold, and animal dander), common food allergens, or both. Here’s what to expect across the major categories.
Environmental and Inhalant Allergens
If you’re dealing with chronic sneezing, congestion, itchy eyes, or asthma flare-ups, your allergist will likely test for airborne triggers. A standard environmental panel covers tree pollens (oak, cedar, cottonwood, pine, olive), grass pollens (timothy grass is the most common marker), and weed pollens like ragweed, sagebrush, and pigweed.
Beyond pollen, the panel includes year-round indoor triggers: dust mites (two species are typically tested), cat dander, dog dander, and mold spores. Alternaria and Cladosporium are two of the most common outdoor molds tested, while Aspergillus is an indoor mold that can be especially problematic for people with asthma. Your allergist may customize the panel based on your region, since pollen types vary significantly by geography.
Food Allergens
Food allergy testing focuses on the nine major allergens recognized in the United States: milk, eggs, peanuts, tree nuts (almonds, walnuts, pecans, and others), wheat, soy, fish, shellfish (crab, lobster, shrimp), and sesame. Sesame was added to this list in 2021 under the FASTER Act. These nine foods account for the vast majority of serious food allergic reactions.
Your allergist may test for additional foods based on your history. If you react after eating stone fruits or certain vegetables, for instance, they might test for those specifically or investigate whether your symptoms stem from a cross-reaction with pollen (a condition called oral allergy syndrome). Food testing can involve skin pricks, blood draws, or both.
Insect Venom Allergies
If you’ve had a severe reaction to a sting, your allergist can test for sensitivity to five specific insect venoms: honeybee, yellow jacket, wasp, yellow-faced hornet, and white-faced hornet. Each venom is tested individually because you can be allergic to one and not the others. This distinction matters because venom immunotherapy (allergy shots) is targeted to the specific insect that caused your reaction, and it’s highly effective at preventing life-threatening reactions from future stings.
Contact Allergens
Contact dermatitis, the itchy rash you get from touching something your skin reacts to, requires a completely different type of testing. Allergists use patch testing, which involves placing small adhesive panels on your back containing common irritants. The standard panel (called the T.R.U.E. TEST) screens for 35 allergens covering 58 individual substances.
The most commonly identified culprits include nickel (found in jewelry, belt buckles, and phone cases), fragrances (a mix of eight compounds like geraniol and cinnamaldehyde), preservatives used in cosmetics and shampoos (parabens, formaldehyde, thimerosal), rubber chemicals found in gloves and elastic, lanolin, hair dye ingredients like p-phenylenediamine, epoxy resin, and certain antibiotics applied to the skin (neomycin and bacitracin). The patches stay on your back for 48 hours, then your allergist reads the results over the next few days to see which substances triggered a reaction.
Drug Allergies
Penicillin is the most commonly tested drug allergy, and it’s also the most commonly mislabeled one. Many people who were told they’re allergic as children turn out to tolerate penicillin just fine when formally tested as adults. Allergists can perform skin testing using a penicillin derivative to detect the immune response, and for people considered low-risk based on their history, a direct oral challenge with amoxicillin may be used instead. Getting a penicillin allergy label removed opens up access to an entire class of effective, inexpensive antibiotics.
Allergists can also evaluate reactions to local anesthetics, certain chemotherapy drugs, and other medications, though the approach varies. Some drugs lend themselves to skin testing while others require a graded oral challenge, where you take increasing doses under medical observation.
How Skin Prick Testing Works
Skin prick testing is the most common method allergists use. Small drops of allergen extracts are placed on your forearm or back, then your skin is lightly pricked through each drop. Results appear within 15 to 20 minutes. A raised bump (called a wheal) that measures 3 millimeters or larger than the negative control is considered a positive result. The test is quick and minimally uncomfortable, more of a scratching sensation than actual pain.
Your allergist will also place a positive control (histamine, which should always cause a bump) and a negative control (saline, which shouldn’t) to make sure your skin is reacting normally. If the negative control causes a bump, the test results are harder to interpret, and your allergist may switch to blood testing instead.
How Blood Testing Works
Blood tests measure the level of allergen-specific antibodies (called IgE) circulating in your blood. Results are reported on a scale from grade 0 to grade 6. A level below 0.35 units is considered negative. Grades 1 and 2 (0.35 to 3.5 units) indicate weak to moderate sensitivity, while grades 4 through 6 (above 17.5 units) represent strong positivity.
Blood testing has one major practical advantage: you don’t need to stop taking antihistamines beforehand. It’s also useful for people with severe eczema (where skin testing is difficult) or for those who’ve had anaphylaxis and shouldn’t be re-exposed to the allergen through the skin. The trade-off is that results take several days to come back, whereas skin testing gives answers in the office.
Oral Food Challenges
When skin and blood tests are inconclusive, or when your allergist suspects you may have outgrown a food allergy, an oral food challenge is the gold standard. You eat small, gradually increasing amounts of the suspected food in the office, with about 15 to 30 minutes between each dose. If no symptoms appear, you’re typically observed for one to three hours after the final dose before being sent home.
If a reaction does occur, the medical team treats it on the spot and monitors you for two to four hours after symptoms resolve. For certain delayed-type reactions (like food protein-induced enterocolitis, where symptoms can take over two hours to appear), the feeding schedule is faster and the observation window is longer.
How to Prepare for Allergy Testing
If you’re scheduled for skin testing, you’ll need to stop oral antihistamines five days beforehand. Nasal sprays should be stopped three days before, and certain other medications two days before. Your allergist’s office will give you a specific list, but the key point is that antihistamines suppress the skin’s reaction and can cause false negatives. Blood testing doesn’t require any medication changes, which is one reason your allergist might choose it if stopping antihistamines would leave you miserable.
Bring a list of your symptoms, when they happen, and any patterns you’ve noticed (seasonal, after eating specific foods, after being around animals). This history is just as important as the test results themselves, because a positive test only confirms that your immune system recognizes a substance. Your allergist combines that information with your symptom history to determine which allergens are actually causing problems and which are clinically irrelevant.