Skin tests are methods of testing for allergic antibodies called specific IgE. A test consists of introducing a small amount of the suspected allergen into the skin and noting the development of a positive reaction (which consists of a wheal, swelling, or flare/redness). The results are interpreted 15 minutes after the application of the allergen. We utilize the following skin test methods:
Prick Testing: The skin is pricked with a plastic device which has been dipped into an extract of allergen.
Intradermal Testing: Small amounts of an allergen are injected into the superficial layers of the skin.
Testing can be performed to important Mississippi airborne allergens, foods (peanuts, shellfish, milk, egg, and others), stinging insects (wasps, bees, fire ants, and others), or certain drugs (penicillin, lidocaine).
Skin testing generally takes only a few minutes. Prick tests are usually performed on the back but may also be performed on the arms. Intradermal skin tests may be performed if the prick skin tests are negative and are performed on the arms. Positive tests consist of a red, raised, itchy bump and will gradually disappear over a period of 30 to 60 minutes, and, typically, no treatment is necessary for this itchiness. Occasionally local swelling at a test site will begin 4-8 hours after the skin tests are applied, particularly at sites of intradermal testing. These reactions are not serious and will disappear over the next week or so.
IMPORTANT THINGS TO REMEMBER
1. No prescription or over the counter oral antihistamines should be used 3 to 5 days prior to skin testing. These include cold tablets, sinus tablets, hay fever medications, over the counter allergy medications such as Claritin, Zyrtec, Allegra, Actifed, Dimetapp, Benadryl, and over-the-counter sleep medicines such as Tylenol PM. Prescription antihistamines such as Clarinex, Xyzal, hydroxyzine, nasal antihistamines such as Patanase, Dymista, Astelin, and ocular antihistamines such as Pataday or Optivar should also be stopped at least 5 days prior to testing. If you have any questions whether or not you are using an antihistamine, lease please ask the nurse or the doctor. In some instances a longer period of time off these medications may be necessary.
2. Prescribed medications such as amytriptyline hydrochloride (Elavil), doxepin (Sinequan), and imipramine (Tofranil) are potent antihistamines and should be discontinued at least 2 weeks prior to receiving skin testing after consultation with your physician. Please make the doctor or nurse aware of the fact that you are taking these medications so that you may be advised as to how long prior to testing you should stop taking them.
3. You may continue to use your intranasal allergy sprays such as Flonase, Rhinocort,
Nasonex, Nasacort. Omnaris, Veramyst, Zetonna, and Qnasl.
Skin testing will be administered at this medical facility with a medical physician or other health care professional present since occasional reactions may require immediate therapy. These reactions may consist of any or all of the following symptoms: itchy eyes, nose, or throat; nasal congestion; runny nose; tightness in the throat or chest; increased wheezing; lightheadedness; faintness; nausea and vomiting; hives; generalized itching; and shock, the latter under extreme circumstances. Please let the physician and nurse know if you are pregnant or taking beta-blockers. Allergy skin testing may be postponed until after the pregnancy in the unlikely event of a reaction to the allergy testing.
Patch testing is generally performed to determine whether a particular substance is causing allergic contact dermatitis. Patch tests can detect delayed allergic reactions, which take several days to develop.
Patch tests don't use needles. Instead, allergens are applied to patches, which are then placed on the skin. These allergens can include latex, medications, fragrances, preservatives, hair dyes, metals and resins.
Patches remain on the back for 48-72 hours. During this time, you should avoid washing the area and activities that cause heavy sweating. The patches are removed when you return to the doctor's office. Irritated skin at the patch site may indicate an allergy.
Subcutaneous Immunotherapy (SCIT)
Subcutaneous allergen immunotherapy, also known as “allergy shots,” may help people who suffer from allergic asthma, rhinitis, conjunctivitis, or stinging insect allergies. Pollen, mold, animal dander, and insect venom are made up of substances called allergens which trigger allergy symptoms upon exposure. The goal of immunotherapy is to decrease sensitivity to allergens.
Numerous studies have shown that SCIT decreases asthma symptoms and can slow the progression of asthma in allergic individuals. It is the only therapy that is disease-modifying rather than just treating the symptoms. SCIT may be helpful for some people with atopic dermatitis (eczema) depending on their sensitivities. It is not currently indicated for food allergies.
While this therapy is not a cure, it may bring long lasting relief of allergy symptoms even after treatment is stopped. It can also be an effective way to reduce symptoms in people who do not wish to take daily medications. It is cost-effective over the long-term due to reduced doctor visits and medications.
How Does It Work?
With allergy shots, increasing amounts of an allergen are given at regular intervals. Over time, the body develops immunity or tolerance to the offending allergen(s), decreasing symptoms when exposed. There are generally two phases to immunotherapy:
- Build-up phase: Weekly injections are given with increasing amounts of the allergens at each visit. The length of this phase generally ranges from 9-12 months.
- Maintenance phase: Once the effective therapeutic dose is reached, there will be longer periods of time between shots, ranging from 2-4 weeks. Patients generally continue SCIT for 2-5 years depending on several factors including history of asthma and response to treatment.
You may notice a decrease in symptoms during the build-up phase, but it may take as long as 6 months on the maintenance dose to notice an improvement. The effectiveness of SCIT appears to be related to the duration of treatment and the dose given.
Reactions to SCIT can include any of the following symptoms: itchy eyes, nose, or throat, nasal congestion, runny nose, tightness in the throat or chest, coughing, wheezing, lightheadedness, loss of consciousness, nausea, vomiting, hives, swelling, generalized itching, and rarely, shock which may be life-threatening.
Where Should Immunotherapy Be Administered?
Adverse reactions to immunotherapy are rare but can require immediate medical attention. This is why immunotherapy must be administered in a medical facility appropriately outfitted with equipment and staff capable of identifying and treating these reactions. You are required to wait in the clinic where you receive injections for 20-30 minutes after each injection.
Sublingual Immunotherapy (SLIT)
The FDA has recently approved several new medications for the treatment of allergic rhinitis known as sublingual immunotherapy (SLIT).
Current “allergy shots” are also known as subcutaneous immunotherapy (SCIT). SCIT works by causing immunologic changes that allow a patient to be exposed to allergens without symptoms. This applies to environmental allergens such as trees, grasses, weeds, molds, dust mites, cockroach, pet danders, and insect venoms. SCIT is effective in treating allergic rhinitis, but is also the only therapy which actually modifies the course of asthma. The major limitations of SCIT are the need for repeated clinic visits and the very rare risk of severe allergic reactions.
How Does It Work?
Sublingual immunotherapy (SLIT) induces tolerance to the offending allergens by the same mechanism as SCIT, but the allergens are given orally in a dissolvable tablet. At this time, there is no known benefit in modifying asthma. These tablets are available for grass and ragweed pollen and are approved for adults up to 65 years of age and in some cases in children as young as 5 years of age. The grass tablets do not treat two of our major southern grasses, Bermuda and Bahia. These tablets are also not helpful for patients with allergies to tree pollen, pet dander, or dust mites. It is not known whether multiple tablets can be taken at the same time.
When Can Immunotherapy Be Helpful?
SLIT is an addition to currently available treatment options for allergic rhinitis and is not a replacement for SCIT. Allergic rhinitis is a complex disease, and not all patients will benefit from SLIT. Discuss with your doctor to find out if this therapy is right for you. Insurance may cover SLIT to some degree.
The major side effects of SLIT are oral itching, throat irritation, mouth swelling, and ear itching. Severe life threatening reactions are rare. The tablets must be taken daily and work best if started 12 weeks before the allergy season. The first dose must be given in a clinic followed by at least 30 minutes of observation. An EpiPen must be kept available at all times in the rare case of an allergic reaction. If several doses of SLIT are missed, the patient must return to clinic to restart the therapy.
Practical Tips For SLIT
- Tablet should be taken once daily
- Tablet should be placed under the tongue, NOT chewed or swallowed whole
- Do not swallow for at least one minute after use
- Do not brush teeth or eat/drink for 5 minutes after use
- Have injectable epinephrine (EpiPen, Auvi-Q) available at all times
- Hold the dose if asthma is unstable/ actively wheezing
- Contact your doctor if several doses are missed
How is it used?
The allergen-specific IgE antibody test is a blood test used to help diagnose an allergy to a specific substance or substances for someone with allergy symptoms. This is especially true if symptoms are recurrent and associated with triggers such as foods or environmental exposures but can also be helpful in diagnosing allergy to insects such as wasps/bees or fire ants.
Skin prick testing is sometimes preferred and frequently more cost-effective, but skin test interpretation can be affected by skin conditions such as dermatitis or eczema, and by medications including antihistamines and antidepressants. With some skin tests there is also the potential for severe or life-threatening reactions such as anaphylaxis. In these cases, the allergen-specific IgE antibody test may be ordered as an alternative, as it is performed on a blood sample and does not have an effect on the person being tested.
What does the test result mean?
Results of allergy blood testing must be interpreted with care. Even if an IgE test is negative, there is still a small chance that a person does have an allergy. Similarly, if the specific IgE test is positive, a person may or may not ever have an actual allergic reaction when exposed to that substance.
With foods, negative results indicate that a person probably does not have an IgE-mediated allergy to the specific allergens tested, but sometimes an oral challenge may be necessary to definitively confirm the food can safely be eaten.
An elevated allergen-specific IgE result indicates that the person tested likely has an allergy. However, the amount of specific IgE present does not necessarily predict the potential severity of a reaction. A person's clinical history and additional tests may be necessary to confirm an allergy diagnosis.
Is there anything else I should know?
Sometimes a health practitioner will look at other blood tests for an indirect indication of an ongoing allergic process, including a total IgE level or a complete blood count (CBC) and white blood cell differential (specifically eosinophils and basophils). Increases in these test results may suggest an allergy, but they may also be elevated for other reasons.
Source: Lab Tests Online
An oral challenge is a procedure performed under medical supervision in which a person takes a food or medication by mouth in order to assure that no allergic reaction occurs. There may be several steps involved, in which increasing doses or amounts of the food or drug are given. There may also be placebo steps in which placebo drugs are given.
Allergic reactions may occur with this procedure, including but not limited to, any or all of the following symptoms:
- Itchy eyes, nose, or throat;
- Nasal congestion;
- Runny nose;
- Tightness in the throat or chest;
- Coughing or wheezing;
- Lightheadedness or loss of consciousness;
- Nausea and vomiting;
- Hives or generalized itching;
- Low blood pressure;
- Shock, under extreme conditions.
Reactions can be serious, and rarely, fatal. If the patient is 17 years of age or younger, a parent or legal guardian must be present during this time. The patient's vital signs and clinical status will be monitored periodically throughout the procedure. If the patient develops a significant reaction, treatment may include oral/intramuscular steroids, antihistamines, and possibly injectable epinephrine. If the reaction is severe enough, transport to the nearest emergency facility may be necessary.
This procedure is recommended to ensure the patient does not have an allergy to the offending agent, but is not strictly required, and avoidance of the offending agent can be continued.