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How to Identify Allergy Triggers

Diagnosing patients with allergies isn’t as easy as it seems, but it is generally simple. While allergy triggers can vary, the processes for diagnosing the exact allergy are fairly straightforward. Some can be done by the patient at home but take time, while others need laboratory evaluations but are fairly fast. Here’s a look at five ways to identify allergy triggers.


This is usually used for potential food and skin allergies. The patient needs to start eliminating various foods and cosmetics/cleaning substances from his or her life, gradually adding them back in. For example, someone who has noticed a rash popping up more often after the person eats shellfish needs to eliminate all shellfish, any derivatives from shellfish, and anything that could be contaminated by shellfish for several days (10 days to 2 weeks is a common time period). If the rash clears up, the patient adds one specific food back in and waits another few days to see if the rash comes back. As you can see, this can take a long time and be easily derailed if the patient accidentally eats one of the test foods at the wrong time.

Location and Season History

This is a fairly simple procedure, but it takes a long time. Basically, the patient has to notice when and where the allergy occurred. Sometimes the result is inconclusive, and the patient has to have more specific tests done. But many times, the patient can quickly figure out if the problem has to do with a pet, a dwelling (e.g., one with a mold problem), or a seasonal pollen. This method will not distinguish between true allergic rhinitis and vasomotor rhinitis, but it can show the patient what he or she needs to avoid.

Skin Prick Test

This is the basic lab test done for allergies initially and is read by the doctor or nurse in the same lab or office. Note that it works for IgE-based allergies only. It can test for food, medication, and environmental allergies — pretty much anything that can be turned into an extract or administered via needle. A small amount of the suspect substance is placed just under the top skin layers with a needle, along with a glycerin control test spot. The reaction of the skin to the substance, and that reaction compared to the reaction to the glycerin, tells you whether an allergy is present. Note that hidden skin conditions like dermatographia can make this difficult; if the person reacts to the glycerin, too, the test becomes unreadable.


This is a blood test given when skin tests are not readable or doable. A blood sample is used to detect antibodies to allergens. The blood sample is not tested immediately unless there are no other tests in line for evaluation, so it can be a couple of days before results show up. This is another IgE-only test.

Biopsy and Other Invasive Tests

For allergies caused by antibodies other than IgE, a biopsy or other invasive test may need to be done.

Whether you send RAST samples out to another lab or have an attached lab department with techs who can administer skin prick tests, having a good lab that can accurately evaluate test results is crucial when it comes to allergies. Ensure that your patients receive the correct diagnosis by choosing your lab carefully.


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