Latex Allergy Desensitization by Exposure Protocol..(Part 2)

Allergy skin tests: Identify the sources of your sneezing.

For more than a century, doctors have used skin tests to help diagnose allergies. During these tests, your skin is exposed to allergy-causing substances (allergens) and then is observed for signs of an allergic reaction.

Results.

According to the inclusion criteria, the prick test with latex extract and the anti-NRL IgE radioallergosorbent test were positive in all subjects, whereas the patch tests were negative. The results of contact provocation tests and the mucous challenges were positive in all patients as well. These data are consistent with the occurrence of an IgE-mediated (Type I, immediate) allergy to latex.

Along with your medical history, skin tests can confirm whether signs and symptoms, such as sneezing, wheezing and skin rashes, are caused by allergies. They can also identify the specific substances that trigger allergic reactions. Such information can help your doctor develop an allergy treatment plan that may include allergen avoidance, medications or allergy shots (immunotherapy).

The prick test with corn was negative in all the investigated subjects. No dermographism was present. The results of prick tests with food allergens (prick-by-prick method) were positive in some patients, both in treated and control subjects.p>

The contact desensitization protocol was successfully completed in all treated patients, with no remarkable side effects.

Skin testing is widely used to diagnose allergic conditions such as hay fever, allergic asthma and dermatitis (eczema). It's safe for people of all ages, including infants and older adults.

After the 12-mo treatment, all patients could wear latex gloves on both hands for more than 1 h daily, with no side effects. This fact was particularly important for professional health care workers with latex-induced occupational allergy, who are supposed to use latex gloves daily.

Blood tests (in vitro allergen-specific IgE antibody tests) are particularly useful for those who should not undergo skin tests. Although blood tests can be as accurate as skin tests, they're not performed as often because they may be less sensitive and are more expensive. If you want to start immunotherapy — a series of injections intended to increase your tolerance to allergens — you need either a skin or blood test to identify the specific substances that trigger your allergies.

All the patients, at the end of the treatment, could stay in an environment where they were exposed to latex inhalation. The desensitization treatment also resulted in a clinical improvement of the associated cross-reactions, because Patients 1, 3, and 4 could eat again melon, fresh tomato, or banana and pineapple without any clinical symptoms.p>

The mucous challenge, performed to better confirm the occurrence of a complete desensitization, had negative results in all treated subjects.

Before recommending a skin test, your doctor will ask detailed questions about your medical history, your signs and symptoms, and your usual way of treating them. Your answers can help your doctor determine if allergies run in your family and if you might also have them.

Moreover, Patient 3 became pregnant after the desensitizing treatment and successfully delivered a baby. During pregnancy and delivery, the patient was always examined and assisted by latex-glove-wearing medical staff, and she had no allergic reactions.p>

After the desensitization, the allergological examination showed a marked reduction of the cutaneous response to latex antigens.

Next, your doctor will perform a physical examination to search for additional clues about the causes of your signs and symptoms.

The mean diameter of the wheal of the prick test with latex standard extracts (dilution 1:100) decreased from 9 to 4 mm in Patient 1, from 10 to 5 mm in Patient 2, and from 10 to 3 mm in Patient 3. Also, the reactions to prick tests to food allergens were markedly decreased after desensitization to latex (from 7 to 3 mm to tomato and from 5 to 2 mm to melon in Patient 1; from 8 to 4 mm to banana in Patient 3; and from 5 to 2 mm to pineapple in Patient 4).p>

Your medical history and physical examination may provide enough information for your doctor to discuss your diagnosis and treatment. If so, a skin test may be unnecessary. But if your doctor is uncertain that you have allergies or suspects that you have allergies and needs more information about the possible causes, he or she may recommend that you have a skin test.

An almost 40% decrease in specific IgE levels was observed after treatment (from 9.48 ± 2.32 to 5.86 ± 2.62 U/mL; mean ± SE). However, such a difference did not reach statistical significance (paired Student’s t-test), probably because of the reduced number of subjects investigated. The values of total IgE did not show significant changes after desensitization (from 204.5 ± 68.1 to 190.3 ± 92.5 U/mL).p>

No significant variation in specific IgG4 levels was observed after treatment.

Before scheduling a skin test, your doctor will need a list of all your prescription and over-the-counter medications. Some medications can suppress allergic reactions so that the skin testing can't be performed. Other medications may increase your risk of developing a severe allergic reaction during a test.

All control subjects still exhibited a positive contact and mucous challenge with latex, as well as positive latex (and specific food) prick tests, at the end of the 1-yr follow-up period. Serum values of total and specific IgE levels did not significantly vary in control subjects after the follow-up period.

Because medications clear out of your system at different rates, your doctor may ask that you stop taking certain medications for up to 10 days. Medications that can interfere with skin tests include.

Discussion.

Until now, the principal therapeutic approach to latex allergy was to avoid exposure to latex. However, this seems particularly difficult because of the ubiquity of latex-containing products, their similarity to nonallergenic synthetic rubber products, and often inadequate and sometimes misleading product labeling.p>

Skin testing is usually performed in a doctor's office. Typically, a nurse administers the test and a doctor interprets the results.

Moreover, because the transmission of blood-borne diseases is one of the most pressing public health concerns, the use of (often latex-containing) gloves and condoms is essential to reduce the risk of sexually or blood-transmitted diseases. Current efforts by industry and by the Food and Drug Administration aim at reducing the antigenicity of medical latex products, although it is doubtful that any latex product could be made 100% antigen free.p>

Contrary to what you may have heard, skin tests cause little if any discomfort. Because the needles used in these tests barely penetrate your skin's surface, you won't bleed or feel more than mild, momentary discomfort.

Sensitized health care workers are encouraged to wear low-protein, powder-free gloves. However, the protective effect of some alternative gloves is controversial, and some of them are unacceptable to surgeons because nonlatex gloves generally do not have the same mechanical characteristics as latex ones and therefore do not provide an accurate "touch."p>

Some tests detect immediate allergic reactions, which develop within minutes of exposure to an allergen. Other tests detect delayed allergic reactions, which develop over a period of several days.

There are two recent reports dealing with patients experiencing allergy to latex who underwent a subcutaneous specific desensitization. However, many patients developed important side reactions during the treatment which required the use of epinephrine or steroids.p>

A puncture, prick or scratch test checks for immediate allergic reactions to as many as 40 different substances at one time. In adults, the test is usually done on the forearm. Children are usually tested on the upper back.

Our patients are the first to be treated with a contact desensitization. The adopted protocol seems to be very effective, because after treatment, patients with demonstrated allergy to latex could tolerate exposure to latex without any symptoms.

After cleaning the test site with alcohol, the nurse draws small marks on your skin and applies a drop of allergen extract next to each mark. He or she then uses a sharp instrument (lancet) to introduce the extracts into the skin's surface. A new lancet is used for each scratch to prevent cross-contamination of allergens. The drops are left on your skin for 15 minutes, and then the nurse observes your skin for signs of allergic reactions.

The proposed contact desensitization protocol seems absolutely safe (even though we treated only a few patients), and no side effects were reported. Moreover, we reported a slight decrease of serum-specific IgE to latex in treated patients, together with a reduction of prick test results as already observed during conventional subcutaneous hyposensitizing treatment (for instance, in respiratory allergy); instead, contrary to what is observed during conventional immunotherapy, specific IgG4 (blocking antibodies) did not show any modification.

You may need a more sensitive immediate-reaction test — known as an intradermal test — if a puncture, prick or scratch test is inconclusive. During this test, a nurse uses a thin needle and syringe to inject a small amount of allergen extract just below the surface of the skin on your arm. Then he or she inspects the site after 15 minutes for a local skin reaction.

We cannot explain this fact, but we think it can be caused by the route of the administration of the allergen, which probably requires more time to produce modifications of the immune system.p>

The only drawback of the adopted protocol seems to be the relatively long time—12 months—required for desensitization. However, the method is very simple and, because of its complete safety, may be easily performed by the patient at home with just a periodic control by experienced allergological staff.p>

Patch tests detect delayed allergic reactions. During a patch test, your skin may be exposed to 20 to 30 extracts of substances that can cause contact dermatitis. Caustic substances — such as industrial solvents — are diluted to prevent skin damage.

In the last 15 years, to reduce the frequency and severity of potential side effects of conventional subcutaneous immunotherapy, many alternative desensitization methods have been proposed in allergic patients; these methods are based on the oral, nasal, sublingual, or bronchial introduction of the specific allergen. The effectiveness and the safety of sublingual desensitization have been confirmed in controlled, double-blinded studies.p>

Allergen extracts are applied to bandages that you wear on your arm or back for 48 hours. During this time, you should avoid bathing and activities that cause heavy sweating. The bandages are removed when you return to your doctor's office for an evaluation.

There are no data concerning desensitization treatments performed by percutaneous administrations of the allergen (neither latex nor other allergens). However, a satisfactory transcutaneous absorption may be hypothesized for many allergens, because many drugs have a well known transcutaneous absorption.p>

Before you leave the doctor's office, you'll know the results of a puncture, prick or scratch test or an intradermal test. A patch test may take several days or more to produce results.

On the basis of experimental observations on mice, sensitization to protein allergens and even immediate-type allergy may develop transcutaneously. Moreover, a transcutaneous immunization has also been demonstrated in humans.

If an allergen provokes an allergic reaction to a puncture or intradermal skin test, you'll develop a raised, red, itchy bump (wheal and flare) that may look like a mosquito bite. A nurse will then measure the bump's size.

A desensitization might be performed by means of the percutaneous administration of a specific antigen. In this way, the adopted contact desensitization may act exactly as the conventional subcutaneous desensitization, the only difference consisting of a different route of the allergen administration.p>

After the nurse records the results, he or she will clean your skin with alcohol to remove the marks and allergen droplets. Then you'll meet with your doctor to discuss the results and possible treatment options.

After a long period of absence of any exposure to a specific allergen, positive allergological tests may spontaneously turn negative in the absence of any treatment. However, in our opinion, the occurrence of a complete desensitization to latex cannot be explained by a spontaneous "natural course" of latex allergy in our patients, who had professionally repeated exposure to latex allergens in the months preceding the desensitization, and, of course, during the whole desensitization period.

A positfde skin test means that you may be allergic to a particular substance. Bigger bumps usually indicate a greater degree of sensitfdity. A negatfde skin test means that you probably aren't allergic to that particular allergen.

Moreover, such a spontaneous desensitization did not occur in any of our control subjects, who still exhibited allergy to latex at the end of the one-year follow-up period without contact with latex-containing items.p>

In conclusion, although this study has been completed in only five patients, it provides evidence that a safe therapeutic approach to latex allergy is possible.

The accuracy of skin tests can vary. You may react differently to the same test performed at different times. Or you may react positfdely to a substance during a test but not react to it in everyday life... [read more]

Contact desensitization seems to be safe even in patients with latex-induced occupational asthma, in which the application of latex to skin can induce asthmatic responses. However, further studies in larger groups of patients are necessary to fully confirm these preliminary results and to assess whether this technique can be successfully applied to treatment of allergic responses to other environmental allergens.