What Does Diagnosing Allergies Involve?

There are many ways to go about diagnosing allergies. Let's see what is the standard procedure used for the main types.
What Does Diagnosing Allergies Involve?

Written by Josberth Johan Benitez Colmenares, 23 August, 2021

Last update: 23 August, 2021

Diagnosing allergies can be challenging for allergists. Although in some cases, the exact trigger can be determined, in others, it may take several months and even years before the patient is referred to a specialist. Many are also wary of going to the doctor, even when their symptoms are acute.

It’s important for you to seek medical assistance to determine what’s causing the symptoms you’re experiencing. When the catalyst is detected, the allergist can initiate a personalized treatment and recommend some habits to reduce the episodes. Today, we’ll go over the basic protocol that’s followed in order to detect allergic reactions.

Self-tests for diagnosing allergies

Diagnosis of allergies begins with self-examination
The first step in treating your allergy problem is simply identifying it. Paying attention to the symptoms and their possible triggers is of the utmost importance.

Often, the patient suspects that they have an allergy when they associate the appearance of certain symptoms with some catalysts. For example, you may notice that the body swells after eating a certain food group or that you develop a stuffy nose, irritation, and watery eyes after touching an animal.

Watching for patterns is the first step in diagnosing allergies. You can keep a journal to keep track of what you ate, touched, or did before the outbreaks appeared, something that will be of great help for the specialist in your first medical visit. If you want, you can also use a home test.

There are dozens of tests available, each designed to measure sensitivity to different allergens. Studies support their use for initial screening, although this should always be corroborated in a clinical setting. Keep in mind that home tests are less accurate and can give false negatives more often.

Skin tests for the diagnosis of allergies

The real allergy diagnosis process begins with your visit to an allergist. As indicated by the American College of Allergy, Asthma & Immunology, it all begins with reviewing the patient’s history and symptoms. In this sense, the doctor will proceed with the following:

  • Evaluating the clinical history–the patient’s personal history of allergies as well that of their family
  • Checking for the presence of underlying diseases
  • Analyzing the symptoms, if they’re visible, and ruling out certain possible explanations

After this, you’ll start with a skin test. Skin tests are still considered the gold standard for detecting allergic reactions. There are many types. According to the Asthma and Allergy Foundation of America, the most common are the following:

A prick or puncture test

This is the most accurate, quick, and affordable method of determining allergies in patients. It’s done by placing a small sample of the allergen on the surface of the skin. Then, a specialist pricks it with the help of a needle so that part of it enters superficially.

Then, the specialist will wait for several minutes and check for possible reactions that occur in the punctured area. Usually, 15 minutes is enough, although it may be longer depending on the specialist’s criteria.

A positive result is obtained when a raised welt forms over the puncture site. This test by itself isn’t capable of determining all types of allergies or their severity.

Intradermal skin test

If there are doubts regarding the previous examination or conclusive results haven’t been obtained, the specialist can do an intradermal skin test. This consists of injecting a small amount of the suspected allergen under the skin so that it travels a little deeper than in the previous case.

It’s very useful for diagnosing allergies to drugs or similar substances. It can be of little use, on the contrary, in the case of food allergies. This procedure can yield more false positives, so it must be interpreted in context.

Patch testing

If no outbreaks have been found based on previous tests, but allergens are still suspected, then special patches can be used. These contain a small sample of the trigger and are placed on the skin for 24 to 48 hours to assess the result through prolonged exposure. It’s useful for a variety of conditions, especially contact dermatitis.

Laboratory tests for diagnosing allergies

Diagnosis of allergies includes blood tests
Although laboratory tests for allergies are very important, they sometimes tend to be nonspecific, since identifying the allergen by these means is difficult.

As a complement to the above, laboratory tests will be carried out. The above procedures can detect the reaction but don’t provide the specialist with complete information. Therefore, they’ll choose to do the following:

  • Blood tests: Evidence supports their use to determine immunoglobulin E (IgE) values for allergens such as food, latex, medications, inhalants, and poisons. For this, they can perform several studies, although the ELISA test and the ImmunoCAP are the most used.
  • Exposure test: In a controlled environment, the specialist will give the patient a sample of the allergen to inhale or ingest. This is done under timed intervals and with anticipation of a possible anaphylactic reaction, as Food Allergy Canada points out.

This last test should only be done by a professional. Avoid exposing yourself to triggers due to the risk of a severe allergic reaction (anaphylaxis). Exposure testing is especially helpful in detecting food and drug allergies.

Differential diagnosis of allergies

The symptoms that you’ve perceived have many possible explanations that aren’t related to allergies. These vary for each condition, so listing them here would be very lengthy. However, we’ll highlight some of the main ones:

  • Infectious triggers (like a virus, for example).
  • Rare systemic conditions (sarcoidosis, cystic fibrosis, and so on).
  • Compromised mechanical structural factors (a deviated septum, adenoid hypertrophy, and others).
  • Ulcerative colitis, irritable bowel syndrome, Crohn’s disease, and other gastrointestinal conditions.
  • Psoriasis

Other possible explanations are cases of intoxication, cold, or intolerance. It all depends on the symptoms you’re presenting. To rule out other explanations, you must go to the specialist and start the diagnostic process. With medication and certain changes in your lifestyle, you can reduce the episodes and counteract the signs.

It might interest you...
Differences Between Allergies and Colds
Muy SaludRead it in Muy Salud
Differences Between Allergies and Colds

Despite the confusion, there are several differences between allergies and colds. Today we'll show you how to distinguish them.



  • Siles RI, Hsieh FH. Allergy blood testing: A practical guide for clinicians. Cleve Clin J Med. 2011 Sep;78(9):585-92. doi: 10.3949/ccjm.78a.11023. PMID: 21885690.
  • Winn AK, Salo PM, Klein C, Sever ML, Harris SF, Johndrow D, Crockett PW, Cohn RD, Zeldin DC. Efficacy of an in-home test kit in reducing dust mite allergen levels: results of a randomized controlled pilot study. J Asthma. 2016;53(2):133-8.