What is Allergy Skin Testing?

Allergist Las Vegas administrating an allergy test on man's arm

If you suspect that you have allergies, your doctor can perform several different tests to confirm a diagnosis and determine exactly what you’re allergic to. One option is skin testing, which is also called scratch testing. Scratch tests are the most common way to check for certain allergies such as food and pollen. Once a diagnosis is made, your allergist will recommend the best course of treatment.

What is Scratch Testing?

Scratch testing is a simple and quick method of allergy testing. It is a tried-and-true method of checking for allergies that has been used for over 100 years. While technology has changed over time, the goals of a skin test remain the same. The test may be performed by either an allergist or a nurse. The practitioner will put a small bit of one or more substances on your skin, which is usually either your forearm or back. Then, he or she will lightly prick the surface layer of your skin or gently scratch the skin’s surface to see if an allergic reaction develops.

Allergist Las Vegas getting a man's arm ready for an allergy test
Allergist Las Vegas completing a skin test on a patient

Signs of an Allergy

If you are allergic to a certain substance, your skin will develop a reaction to the allergen. Reactions typically start to appear in about 15 minutes following exposure. The affected skin may appear to be slightly red or itchy. You may also notice some swelling in the area. Symptoms will gradually subside about 30 minutes to several hours afterwards.

What Allergies Do Skin Tests Cover?

A skin test can check for specific allergies including:

● Environmental allergens (such as grass, weed, trees, molds and animals)

● Foods

● Medications

Depending on the allergy in question, a doctor may perform some additional tests to rule out an allergy. If a food allergy is suspected, for instance, an allergist may also conduct a food challenge test. Blood tests may also be performed if an allergy produces severe reactions that might make a food challenge unsafe.

Allergist Las Vegas with allergy vial

What if Results are Negative?

Sometimes, skin testing may not produce allergic reactions. If your doctor still suspects an allergy, further testing may be required. In the event that scratch tests are negative, your doctor may recommend an intradermal test next. An intradermal test is an alternative type of skin

testing where your doctor injects a tiny bit of a suspected allergen just under the skin’s surface using a fine needle. As with a scratch test, allergy symptoms will appear in about 15 minutes with an intradermal skin test. If you do have allergies, your skin will react with a “wheal” and “flare.” The wheal is a red bump that might also be itchy. The flare is the surrounding area of your skin that is also affected by the allergen. Your allergist can determine the severity of your allergy based on the size of the wheal and flare.

Alternative Allergy Tests

Sometimes, your doctor will recommend another type of allergy test in lieu of or in addition to a skin test. That may include a patch test, blood test, or a food challenge test. If you can’t stop taking a medication that interferes with skin test results, your doctor will usually recommend a blood test instead. Food challenges are used to rule out food intolerances and less severe food allergies.

Allergist Las Vegas with checklist about what patient is allergic to

What to Expect During Your Visit

Before your doctor checks for Las Vegas allergies, he or she will perform an evaluation to make sure you are a good candidate for skin testing. Your doctor will review your medical history at your allergy appointment. If possible, try to keep track of your symptoms, including when they started and the severity of your reaction. Those details will give your doctor a better understanding of what you might be allergic to and what kinds of allergy tests will be safest to perform. It’s also important to let your doctor know of any medications that you are taking. Some medications will interfere with the results of a skin test and may need to be stopped before the day of the test.

Are Skin Tests Safe?

Skin tests are generally considered a safe and accurate method of allergy testing. However, tests are conducted in your allergist’s office to make sure that you receive adequate medical supervision in case of a more severe reaction. In rare cases, people develop systemic responses to an allergy test. Notify your doctor right away if the following occur:

● Difficulty breathing

● Fever

● Lightheadedness

● Large rash

● Swelling of the mouth or face

● Trouble swallowing

After the skin testing appointment, your doctor will remove any markings from your skin and clean the area with rubbing alcohol. You may be prescribed a topical cream such as cortisone to reduce the itching and redness. If your testing includes a patch test, you won’t be able to get the affected area wet for a period of time. Your doctor will tell you what activities to avoid, such as swimming and baths, until your next appointment.

Next Steps in Allergy Testing

If your allergy testing shows that you do have an allergy, your allergist will prescribe a treatment plan. Treatments may include medications such as over-the-counter medications and medications for more severe anaphylactic reactions. An allergist can also recommend steps you can take to reduce allergy exposure at home. If you’re allergic to certain environmental allergies, for instance, your allergist might recommend limiting outdoor activities during times of the day when pollen counts are highest and using an air purifier in your home to eliminate indoor airborne allergens. Based on the allergy in question, your allergy specialist may also recommend a treatment called immunotherapy, which involves gradually introducing you to larger amounts of the allergen to help your immune system develop a tolerance. Your doctor will review the options available and create a treatment plan based on your allergy and your personal preferences.

If you’re ready to find relief from your Las Vegas allergies and asthma symptoms, contact our office today. You can schedule an appointment with Dr. Tottori, a trusted and experienced allergist, through our website or by calling (702) 240 4233.

infographic about allergy testing on skin


  1. Claire Masters July 21, 2021 at 7:28 am - Reply

    Thanks for helping me understand that allergy testing is safe and that doctors will be there to supervise me. My boyfriend and I are very adventurous when it comes to food. We love to travel to try new dishes but we are afraid of the possibility of eating a dish we are allergic to. I’ll suggest we get tested soon.

  2. Shammy Peterson January 5, 2022 at 2:21 am - Reply

    You made a good point when you said that allergy tests must be done at an allergist’s office to ensure their accuracy. This is something that I will share with a friend who wants to determine what triggers her allergy. She always gets allergic reactions even when she is alone at home, so it will make sense for her to understand what she needs to avoid.

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