Getting an allergy test typically starts with your primary care doctor, who can either perform basic testing in-office or refer you to an allergist for more comprehensive evaluation. The process is straightforward, but the type of test you need, how you prepare, and what it costs depend on what you’re reacting to and how severe your symptoms are.
Start With Your Primary Care Doctor
For common conditions like seasonal allergies, persistent nasal congestion, or mild skin reactions, your primary care doctor can often order a blood test or refer you directly to an allergist. A single consultation with an allergist is useful for confirming a diagnosis, identifying your specific triggers, and getting avoidance advice.
Some situations call for an allergist from the start. If you’ve had a severe reaction (anaphylaxis), suspect a food allergy, react to insect stings, or need to determine whether you’re allergic to a medication, an allergist provides diagnostic tools that a primary care office typically doesn’t have, including skin testing, oral food challenges, and drug desensitization. You don’t always need a referral to see an allergist. Many accept self-referrals, though your insurance plan may require one for coverage.
Types of Allergy Tests
Skin Prick Test
This is the most common test and checks for immediate allergic reactions to up to 50 substances at once. A nurse or technician places tiny drops of allergen extracts on your forearm or back, then lightly pricks the skin so the extract enters just below the surface. Results appear within 15 to 20 minutes. A raised bump (called a wheal) 3 millimeters or larger than the negative control spot counts as a positive result. Skin prick testing is the standard method for identifying allergies to pollen, mold, pet dander, dust mites, and foods.
Blood Test
A blood test measures the level of allergy-related antibodies (IgE) your immune system produces in response to specific triggers. It’s a good option if you can’t stop taking antihistamines, have a skin condition like severe eczema that would interfere with skin testing, or have a history of severe allergic reactions that make skin testing riskier. Results take a few days rather than minutes. In Medicare data, the average cost per patient for blood testing was about $161, compared to $247 for skin prick testing.
Patch Test
Patch testing identifies delayed allergic reactions, the kind that develop over several days rather than minutes. It’s primarily used for contact allergies, like reactions to nickel, fragrances, or preservatives in skin products. Adhesive patches containing suspected allergens are placed on your back and left for 48 hours, then read by your doctor at a follow-up visit.
How to Prepare for Skin Testing
Several common medications suppress the skin’s allergic response, which can produce false negatives. You’ll need to stop antihistamines before your appointment. This includes obvious ones like cetirizine (Zyrtec), loratadine (Claritin), and diphenhydramine (Benadryl), but also less obvious medications. Certain stomach acid blockers like famotidine (Pepcid) and cimetidine (Tagamet) have antihistamine properties and need to be paused. Antihistamine nasal sprays and allergy eye drops also interfere with results.
Some antidepressants and psychiatric medications can also suppress skin test reactions and should be stopped one week before testing. However, stopping these medications abruptly can cause withdrawal symptoms, so talk to the prescribing doctor before making any changes. Herbal supplements like nettle and quercetin can also blunt the skin’s response.
Your allergist’s office will give you a specific list of what to stop and when. Blood tests don’t require stopping any medications, which is one reason they’re sometimes preferred.
Testing Children and Infants
Children can be allergy tested at any age, including infants as young as 4 to 6 months. Both skin prick tests and blood tests work in young children. That said, the American College of Allergy, Asthma & Immunology recommends testing be done “judiciously” in infants, meaning there should be a clear clinical reason, like a reaction to a specific food, rather than screening broadly without symptoms.
Safety During Testing
Skin prick testing is very safe. A six-year study tracking an estimated 31,000 patients at a UK allergy clinic found that systemic reactions (symptoms beyond the test site) occurred in just 0.077% of cases, or roughly 1 in 1,300 patients. Seventy-five percent of those reactions were triggered by food allergens. Comparable U.S. studies found even lower rates, between 0.02% and 0.03%. Allergist offices are equipped to treat anaphylaxis on the rare occasion it occurs, which is one reason skin testing is done in a clinical setting rather than at home.
What About At-Home Allergy Test Kits
At-home kits sold online fall into two categories, and the distinction matters. Some kits measure IgE antibodies (the same marker used in clinical blood tests) and send samples to a lab for processing. These can detect sensitization to specific allergens, though they lack the clinical interpretation an allergist provides, meaning you get numbers without the context of your symptoms and medical history.
The more problematic kits measure IgG antibodies to foods, marketed as tests for “food sensitivities” or “food intolerances.” Both the American Academy of Allergy, Asthma & Immunology and the Canadian Society of Allergy and Clinical Immunology recommend against IgG food testing. The presence of IgG antibodies to food is a normal immune response to eating, and higher levels may simply reflect tolerance to those foods rather than a problem. The studies used to promote these tests are often outdated, published in non-reputable journals, or don’t even use the IgG method being sold.
Cost and Insurance Coverage
Most health insurance plans cover allergy testing when it’s ordered by a physician for a documented medical reason. Coverage policies vary, though. Some insurers cover both skin testing and blood testing equally, while others only cover blood testing when skin testing is contraindicated. In plans with equal coverage for both methods, patients averaged about $251 in total testing costs per person, compared to $271 in plans that restricted blood test coverage.
Without insurance, expect to pay more. Skin prick testing typically costs more than blood testing because it involves an office visit, the test itself, and a waiting period for observation. If you’re concerned about cost, ask your allergist’s office for an estimate before your appointment, and confirm with your insurer whether a referral is needed for coverage.
Understanding Your Results
A positive allergy test means your immune system produces antibodies to that substance. It does not automatically mean that substance causes your symptoms. This is why allergists interpret results alongside your history. Someone might test positive for cat dander on a skin test but never experience symptoms around cats. Conversely, a negative test in someone with clear allergic symptoms might prompt further investigation with a different testing method.
For skin prick tests, the size of the wheal gives some information about the degree of sensitization, with larger reactions (over 8 mm) generally correlating with stronger sensitivity. But wheal size alone doesn’t predict how severe a real-world reaction would be. Your allergist uses the full picture, your symptoms, exposure history, and test results together, to build a treatment plan that might include avoidance strategies, medication, or immunotherapy.