Allergy skin test: preparations, types

If you experience frequent itching and see a rash on your skin, this is a possible sign of an allergic skin reaction. Allergy symptoms are similar to other diseases. Because of this, you may need to undergo various skin allergy tests. Anything?

Why is this allergy test done?

Basically, an allergy test is done to find out what compounds can cause an allergic skin reaction. Your doctor may order a skin allergy test if you suspect:

• allergic rhinitis and asthma symptoms that cannot be treated with medication,
• hives and angioedema,
• food allergies,
• skin rash, the skin becomes red, feels sore, or swells after exposure to something, as well
• penicillin allergy and poison allergy.

This allergy check is actually quite safe, both for adults and children. However, in certain cases, this test is not recommended, such as:

• have had a severe allergic reaction (anaphylaxis),
• take medications that can affect the test results, such as antihistamines, and
• have certain skin diseases, such as severe psoriasis.

If this happens to you, your doctor may recommend other types of allergy testing. For example, a blood test (IgE antibody) can be another alternative for those who cannot have a skin allergy test.

Preparations before the skin allergy test

Generally, before the quilt allergy test is performed, the doctor will ask questions about your medical history, from symptoms to family history of illnesses. This aims to make it easier for doctors to determine the cause of allergic skin reactions.

In addition, your doctor may advise you not to take certain medications. The following are medicines that need to be avoided before doing an allergy test so as not to affect the test results.

• Antihistamines, both over-the-counter and from doctors, such as loratadine.
• Tricyclic antidepressants, such as nortriptyline and desipramine.
• Medicines for heartburn, such as cimetidine and ranitidine.
• The asthma drug omalizumab, which can interfere with test results.

Types of skin allergy tests

In general, the skin allergy test is done in a doctor's consultation room with the help of a nurse. This examination will take approximately 20-49 minutes.

Some types of tests can detect an allergic reaction immediately. Meanwhile, another way is delayed allergy testing, which will develop over the next few days. Here are some types of testing for allergic skin reactions that you should know about.

1. Skin prick test (skin prick test)

Skin prick test or a skin prick test is a test used to detect allergens that trigger an allergic reaction. This one allergy test is usually used for patients with food allergies, latex allergies, and allergies to insects.

In adults, the examination will be carried out on the forearm. Meanwhile, a skin prick test will be performed on the upper back in children.

Normally, this test is painless. This is because the needle that is injected does not penetrate the surface of the skin, so you don't bleed or feel pain. Here are the stages skin prick test .

• The doctor will clean the area of ​​the skin to be pricked.
• The nurse injects a small amount of the suspected allergen extract.
• The skin will be scratched so that the allergens get under the surface of the skin.
• The doctor observes skin changes to check for an allergic reaction.
• The reaction results from this examination can be seen 15-20 minutes later.

Apart from the extract that causes skin allergies, there are two additional substances that are rubbed onto the surface of your skin to see if the skin reacts normally, namely:

• histamine, and
• glycerin or saline.

The skin prick test is safe and effective. However, there are times when these allergy tests come out with false positive or negative results.

This can happen if skin prick test placed too close, that is, at a distance of less than two cm. As a result, the allergen solution may mix with other test areas.

2. Skin injection test (skin injection test)

Unlike the skin prick test, this skin allergy test will inject the suspected allergen extract under the surface of the skin.

After 15-20 minutes have passed, the forearm or upper back area will be examined. Generally, the most common allergic reaction is a rash accompanied by swelling and redness.

The skin injection test tends to be more sensitive than the skin prick test. However, this method is considered to produce a more definite reaction.

3. Patch skin test (skin patch test)

Patch skin test is a skin allergy test that is done to detect allergic contact dermatitis.

Unlike the previous two tests which involved a syringe, the skin patch test uses a patch or special patch that is affixed to the back. The patch has been given a small amount of allergen extract, such as:

• latex,
• drugs,
• preservative,
• hair dye, and
• metal.

After the patch has been plastered on the back, the doctor will cover the patch with hypoallergenic tape. The patch will be removed 48 hours after the examination is carried out.

During the 48 hours, you will be asked not to shower and avoid activities that cause your body to sweat. Then you will return to the doctor to open the patch and see the allergy test results.

Keep that in mind skin patch test not used to test for urticaria (hives) or food allergies.

Skin allergy test side effects

The skin allergy test is quite safe. However, it is possible that you may experience certain side effects after undergoing the examination.

The most common side effects are slightly swollen, red skin and an itchy lump. These lumps may become visible during the test.

However, there are some people who experience the mentioned side effects several hours to several days after the examination.

Skin test rarely causes immediate, severe allergic reactions. However, you should do this allergy test in the doctor's office, a place that has equipment and medicines if something goes wrong.

How to read skin allergy test results

After a skin allergy test is done, the doctor will usually conclude some provisional test results. This is because some tests, such as the skin patch test, require waiting 2-3 days for you to consult your doctor again.

Negative test result

A negative allergy test generally does not show any skin changes in response to the allergen. This means that you are not allergic to compounds given by your doctor.

However, there are times when a person has a negative result and is still allergic to the compound given.

Positive test results

If the skin reacts to a substance, it will usually be characterized by a red rash accompanied by bumps. This most likely means that you experience symptoms of allergies to the skin due to exposure to the substance given.

If the reaction is stronger, the symptoms will be much more severe, such as itching and skin redness.

In some cases, you can have a positive result after undergoing a skin allergy test. However, it does not have problems with allergens in everyday life.

Allergy skin tests are usually accurate. However, it is possible that the results can be wrong when the allergen dose is too large.