Allergy testing is a procedure to find out if the patient has an allergic reaction to certain substances or objects. Allergy testing can be done in the form of blood tests, skin tests, or with an elimination diet.
Allergies occur when the immune system overreacts to substances or objects that are not actually harmful. These reactions can range from mild symptoms, such as sneezing, runny nose, or nasal congestion, to severe, life-threatening symptoms, namely anaphylaxis.
Types of Substances that Cause Allergies (Allergens)
There are three types of allergens that commonly cause allergies, namely:
- Inhaling allergens
An inhaled allergen is a type of allergen that triggers an allergic reaction when it enters the nose, throat, or lungs. These types of allergens include dust, pollen, and animal dander.
- Contact allergens
This type of allergen triggers an allergic reaction in the body when it interacts with the skin. Some examples of contact allergens are nickel, fragrance in soap or perfume, and chemicals, such as latex.
- Gastrointestinal allergens
Gastrointestinal allergens are allergens that trigger an allergic reaction when they enter the digestive system. These allergens are commonly found in foods, such as nuts, seafood, and soy. Certain medications, such as penicillin antibiotics and sulfonamides, are also gastrointestinal allergens.
Allergy Test Indications
Doctors will recommend allergy testing in people who experience the following symptoms:
- sneeze
- Runny nose or stuffy nose
- Watery and itchy eyes
- Throw up
- Cough
- Diarrhea
- Hard to breathe
- Wheezing or wheezing
However, these symptoms also need to be accompanied by a suspicion of certain allergens and a family history of allergies, asthma, and eczema.
Allergy Test Contraindications
Blood tests, skin patch tests, and elimination diets are relatively safe for anyone. However, the skin prick test is not recommended for children under 1 year of age, pregnant women, and people with the following conditions:
- Have had a severe allergic reaction (anaphylaxis)
- Suffering from uncontrolled asthma
- Suffering from eczema and psoriasis which cover most areas of the skin on the hands and back
Patients with the above conditions may be advised to undergo allergy testing by other means, generally through a blood test.
Allergy Test Warning
There are several things to consider before undergoing an allergy test, namely:
skin test
- Allergy skin testing should only be done under the supervision of a doctor, because there is a risk of anaphylactic shock during the test.
- Patients who have recently experienced an anaphylactic reaction to an unknown allergen may undergo skin allergy testing for diagnostic purposes. However, it is recommended that the test be performed 4–6 weeks after the anaphylactic reaction occurs.
- Some medications need to be discontinued at least 2 days before the skin allergy test. Therefore, inform all medications and supplements that are being used when consulting with a doctor.
- The doctor may advise the patient not to undergo the skin test and replace it with another test if stopping certain medications would be more risky for the patient.
blood test
- Allergy testing through blood is considered less accurate when compared to allergy tests through the skin. In addition, the results of allergy tests through the blood also come out longer than allergy tests through the skin.
Elimination diet
- Elimination diets can reduce a person's nutritional intake, so its implementation must be supervised by a doctor or nutritionist, especially if it is carried out on children and pregnant or nursing mothers.
Before Allergy Test
Before planning an allergy test, the doctor will ask the patient's and family's medical history, lifestyle and daily activities, and when and why the symptoms appear.
In addition, the doctor will also ask what drugs the patient is currently using. Your doctor may recommend stopping certain medications that could affect test results or risk delaying the procedure you need to undergo. These drugs include:
- Antibody-blocking drugs, such as omalizumab, which are commonly used in patients with severe asthma
- Antihistamines, such as cetirizine
- Beta-blocking drugs, such as atenolol
- Corticosteroid drugs, such as dexamethasone, either in oral or ointment form
- Ulcer medications, such as cimetidine and ranitidine
- Tricyclic antidepressant drugs, such as amitriptyline
- Benzodiazepine drugs, such as diazepam
If necessary, the doctor will also perform a physical examination, to find out whether the patient's complaints are caused by other diseases.
Allergy Test Types and Procedures
There are several types of allergy tests that are commonly done to determine allergens, namely:
Skin prick test
Skin prick test or skin prick test This is the most common type of allergy test. The following are the stages of allergy testing through a skin prick:
- The doctor will mark the skin based on the type of allergen to be instilled.
- The doctor will drip a solution that has been mixed with the allergen onto the patient's skin. At this stage, there are 10–12 allergens that may be instilled based on suspicion of allergy.
- The doctor will prick the area of the skin that has been dripped with the solution with a very thin needle, so that the allergen can enter under the surface of the skin.
- The doctor will watch for signs of allergies that may appear on the skin. If present, an allergic reaction will generally appear within 15-20 minutes.
Intradermal skin test
Intradermal skin test or intradermal skin test usually done if there is a suspicion of allergy to bee stings or certain antibiotics. This test may also be recommended if the patient's skin prick test is negative, but the doctor still suspects that the patient is allergic to an allergen.
In an intradermal skin test, the doctor will inject a small amount of the allergen just under the skin of the patient's arm. After that, the doctor will monitor for 15 minutes to see if there is an allergic reaction in the area of the injection site.
Patch test
Patch test or patch testing This is generally done to detect allergens that cause contact dermatitis. The allergen can be metal, plastic, rubber, or skin cream. Here are the steps of the procedure patch testing:
- The doctor will attach a number of patches or tape to the patient's back. Each patch has been assigned a specific type of allergen that is suspected of causing an allergic reaction in the patient.
- This adhesive should be used for 2 days. During these 2 days, the patient was not allowed to take a bath or do activities that could cause excessive sweating.
- After two days, the patient should return to the doctor. The doctor will remove the adhesive and check for irritation on the patient's back which could indicate an allergic reaction.
Allergy test through blood
The blood allergy test procedure generally takes less than 5 minutes. Allergy testing through blood is done by first taking a sample of the patient's blood. The blood sample will then be taken to the laboratory so that the patient's immunoglobulin E levels can be checked.
Immunoglobulin E (IgE) is an antibody produced by the immune system to fight substances that are considered a threat. When the body experiences an allergic reaction, the amount of IgE will increase.
The measured IgE can be the total number of IgE antibodies in the body (total IgE test) or the number of IgE antibodies that appear in response to an allergen (specific IgE test).
Elimination diet
Elimination diets are performed to detect food allergies. This type of allergy test can be done independently by the patient at home, but it is better to stick with the advice and supervision of a doctor.
The elimination diet procedure takes 5–6 weeks, which is divided into two phases, namely:
- elimination phase (elimination phase)
In the elimination phase, patients can pay attention to whether their symptoms improve or not when the suspected food is stopped. Generally, this phase lasts for 2-3 weeks. If the symptoms do not go away, the patient needs to report it to the doctor.
- The reintroduction phase (reintroduction phase)If during the elimination phase the allergy symptoms disappear, the reintroduction phase can be started. Food reintroduction should be done per each type of food, each within 3 days. During these 3 days, the patient needs to pay attention to the presence or absence of allergy symptoms that appear, such as rash, shortness of breath, or flatulence.
After Allergy Test
Allergy test results through the skin can be known in minutes, except for patch tests. Meanwhile, for allergy testing through blood, it takes several days to wait for the results of the analysis in the laboratory. The following is an explanation of the results of allergy tests:
Allergy test results through the skin
Allergy test results through the skin, namely skin prick test, intradermal skin test, and patch test, are positive if the area of the skin being tested becomes red, itchy, and appears as a pale-colored bump that enlarges in size during the test.
If the skin condition remains normal, it means that the patient does not have an allergy to the allergen used in the test.
Allergy test results via blood
Test results that show the total IgE in the body is higher than the normal limit can indicate that the patient suffers from allergies. However, the total IgE test cannot identify the type of allergen causing the allergy. To find out the type of allergen, the patient must undergo a specific IgE test.
Elimination diet results
If the patient does not experience an allergic reaction during the reintroduction phase, the food is safe for consumption. On the other hand, if an allergic reaction occurs, the cause of the allergy has been identified, so the patient must avoid these foods in their daily diet.
Allergy Test Side Effects and Complications
Allergy testing through blood arguably does not cause serious side effects, except for pain, bruising, or light bleeding at the injection site.
If done according to the procedure, the elimination diet test also has a small risk of causing side effects. However, vulnerable groups, such as children and pregnant women, may experience malnutrition during the elimination phase.
For skin allergy testing, some side effects that may appear after undergoing the test are:
- Itchy rash
- Reddish and irritated skin
- Swelling in the examination area
- Itchy bumps appear on the skin
In some cases, allergy skin testing and the reintroduction phase of the elimination diet can cause an anaphylactic reaction. These conditions include medical emergencies that can be life-threatening for the patient. An anaphylactic reaction can be recognized by the following signs and symptoms:
- Dizzy
- Nausea, vomiting, or diarrhea
- Heart rate is weak and fast
- Skin reactions that include itching and redness
- Difficulty breathing due to narrowing of the airways and swelling of the throat or tongue
If an anaphylactic reaction occurs when you are not in the hospital, contact your doctor immediately or visit the nearest emergency room so that you can get treatment as soon as possible.