How Are Allergies Diagnosed?

Allergies occur when your body mistakes a normally harmless substance for a harmful one, triggering an overactive immune response. These harmless substances are called allergens. Common allergens include pollen food, latex, and insect venom, droppings, saliva, or feces. 

In order to diagnose you with allergies, a healthcare provider will ask questions about your symptoms and medical history to determine a diagnosis. Then they will use tests and procedures to find what triggers the allergy. Allergy tests include skin prick tests, puncture or intradermal tests, and blood tests to check for increased levels of IgE-allergy antibodies. 

The most common type of provider who makes the diagnosis is an allergist or immunologist. These doctors are specially trained in diagnosing and treating allergies and other problems with the immune system. With their help, people with allergies can get answers and access treatments that can improve their quality of life.

Medical History

The first step to diagnosis is gathering information. Your healthcare provider will ask questions about your personal and family medical history. This is because allergies can commonly cooccur with other conditions (such as asthma) and it is more likely you will have allergies if your family members do, as well.

Your provider will also ask about other triggers that could have caused the condition. They need to understand if you have been exposed to any allergens recently. This can help narrow down possible triggers and help them put together a more focused treatment plan.

Your healthcare provider will also consider other factors, such as your age, your occupation, and the severity of symptoms.

Physical Exam

Healthcare providers use physical exams to help them diagnose allergies. During the exam, they look for signs such as redness, swelling, rashes, and itchy bumps, which are all signature symptoms of allergies. They will also listen to your lungs and look inside your nose and throat to see if you’re experiencing any respiratory or nasal symptoms. They can use allergy tests to help confirm your diagnosis once they have a better understanding of what is going on.  

Allergen Testing

Allergy skin testing is a common way to find out if you have allergies. Allergists use this test to see if you are allergic to something. 

Skin tests are a type of exposure test where your allergist puts a very small amount of many different allergens on your skin (usually your arm or back) to see how your body reacts. If you have an allergy, you may have a reaction to one or more of the tested substances. A reaction called a wheal (bump) and flare (redness) will likely appear on your skin. The area around the wheal might be itchy. 

Skin tests help pinpoint which allergen(s) causes a reaction. Skin tests can include several types of testing, such as:

• Skin prick testing (SPT), where a drop of an allergen is placed on your forearm or back. The allergist uses a small probe or tiny needle to scratch the same area. This is not painful and feels like a fingernail scratch.
• Intradermal injection testing, where a small amount of allergen is injected under your skin. This usually is on your forearm.
• Patch tests, where the allergen is taped onto your skin for 48 hours. Your allergist will look at the results about two days later.

Skin testing is a way for providers to learn which things trigger your allergies. This helps them give suggestions about how to avoid the things that will cause problems as well as provide proper treatment if needed.

Blood Tests

Allergists use a type of blood test called a specific IgE (immunoglobulin E) blood test to help diagnose allergies. This type of test measures the concentration of specific IgE antibodies in your blood. It can test for several allergens or triggers such as pollens, mold, food, or animal dander. Immunoglobulin E is a protein created by the immune system to fight off allergens. If high levels of immunoglobulins are detected, then it is likely that you have an allergy. 

Sometimes doctors combine IgE blood testing with skin prick tests in order to diagnose allergies more accurately. The information gathered from these tests can then be used to determine which allergens are causing reactions and if medication or therapies should be prescribed.

Other Testing

Healthcare providers might use other types of tests to help diagnose allergies—namely spirometry and challenge tests.

Spirometry

Allergists may use a test called spirometry in order to detect signs of lower airway restriction or obstruction, especially when you are experiencing symptoms such as coughing, wheezing, and shortness of breath. This type of test measures how much air you can breathe out, as well as how quickly you can do it. People with allergies often have tighter and more restricted lungs, which makes it harder for them to take deep breaths and exhale a lot of air.

By testing the amount and speed of breath, allergists can determine if an allergic reaction is present or not. Spirometry is also useful for detecting other conditions like asthma or chronic obstructive pulmonary disease (COPD), which often occur alongside allergies. 

The results from this test can then be used to help guide treatment plans for people with allergies.

Challenge Tests

Provocation testing is more commonly known as challenge testing. Once an allergist knows that you are experiencing allergies, they use this test to figure out what is causing your allergic reactions. They do this by slowly giving you a tiny bit of allergen at a time during a supervised visit. You are monitored to see if you have any kind of reaction and, if so, how severe it is. 

Challenge testing, or oral food challenge, is often used to help diagnosis of a food allergy. It is considered the gold standard test for food allergies.

Screening for Related Conditions

As mentioned earlier, asthma and chronic lung disease often occur alongside allergies. The tests and exams used to diagnose allergies help your healthcare provider rule out or diagnose these conditions. 

Eczema (also called atopic dermatitis), an inflammatory skin condition, also commonly occurs alongside allergies. This condition is diagnosed with a skin exam. Other more rare conditions might mimic allergies. Your healthcare provider will talk to you about which tests might be needed to rule out other conditions and confirm your diagnosis.

A Quick Review

Allergies are usually diagnosed by allergists or immunologists, who use various tests to determine the cause. Common tests used to diagnose allergies include allergen tests as well as more specialized procedures like spirometry and provocation testing. With help from these tests, allergists can determine the best treatment options for you. 

It's important to partner with your healthcare provider in order to get a rapid diagnosis and create an individualized plan of care. By working together, you and your doctor can help manage your allergies more effectively.