Sublingual Immunotherapy or Allergy Drops: Has its time come?

imageSublingual immunotherapy, also called SLIT immunotherapy, or allergy drops, is slowing gaining acceptance as an alternative to allergy injections for the treatment of common respiratory allergies. Sublingual immunotherapy literally means that the allergy drops are administered under the tongue. However, any oral administration of allergy extract should likely be inferred in the following discussion.

What is immunotherapy?

Immunotherapy, or desensitization, is the cornerstone in the treatment of allergies. Immunotherapy has been used very successfully for many decades. Immunotherapy is the process used to desensitize those who are allergic to airborne allergens, venom from stinging and biting insects, medications, and foods. By far, desensitization to dust mites, mold spores, cat and dog dander, and weed, tree, and grass pollens are the most common allergens for which immunotherapy is recommended by allergists.

Desensitization through immunotherapy is a gradual process which lowers one’s sensitivity to the airborne respiratory allergens responsible for allergic rhinitis (hay fever), allergic conjunctivitis (allergy eyes), and allergic asthma. The process involves introducing to the allergic individual small amounts of substances to which he or she is allergic (allergens) either by injection or orally. Over time, the amount of allergen is gradually increased. Through a complex set of immunologic responses, the immune system develops a tolerance to the allergen. The result of immunotherapy is that when the allergic child or adult is exposed to the allergen, the immune system no longer sees this allergen as foreign, resulting in little or no allergic response.

How does immunotherapy fit into an allergy treatment program?

In spite of the myriads of allergy treatments promoted and espoused to the public, there are only three proven and effective approaches to the treatment of allergies. They are avoidance, medications, and immunotherapy. Depending on one’s specific allergies and severity of symptoms, an allergist might recommend one, two, or all three of these approaches simultaneously.

Even though avoidance of relevant allergens and the use of medications can be very helpful, their purpose is to minimize symptoms. However, neither of these treatment modalities addresses the underlying cause of the allergy.  On the other hand, immunotherapy, or desensitization, is the one and only treatment approach that does address the actual cause, i.e., the immunologic over-reaction that occurs when allergen meets antibody. And, it is in this area that many exciting advances have taken place in the treatment of allergic children and adults, including the availability of sublingual allergy drops, or sublingual immunotherapy.

Allergy shots or allergy drops: What are the advantages and disadvantages?

Immunotherapy is administered in the western world most commonly in the form of injections, known as “allergy shots”. Even though allergy shots or allergy injections are effective and are considered the gold standard of allergy treatment, an allergy shot regimen does have its challenges. Firstly, of paramount importance to the success of allergy shot therapy is compliance. Compliance is directly related to the many logistical issues associated with injection therapy. Allergy shots must be given on a regular schedule, generally starting twice a week for several months, with subsequent weaning to weekly, every other week, every third week, and eventually monthly. The program is commonly recommended for three to five years, and it is critical that there not be a significant lapse of time during the program during which the patient does not receive injections. This schedule adds up to many injections over a long period of time. And, as might be expected, the logistical issues that must be addressed to maintain such an injection schedule results in a low compliance rate for completing the allergy shot program.

Even if compliance and logistical issues of allergy shots can be overcome, immunotherapy can be quite challenging especially in the pediatric population, the population which could and should benefit most from desensitization. Even though the injections are generally not painful, children are inherently fearful of injections, and despite coaxing and sometimes bribing, parents rightfully give up on the idea after several traumatic attempts.

Also of significant concern is the potential for a serious allergic reaction to an allergy shot, albeit infrequent. Whether it is the first injection administered or a random injection a year or two into the course of therapy, the potential always exists of one reacting to an allergy shot. It is for this reason that allergy shots should never be taken at home. They must always be administered under the supervision of an allergist and in a facility equipped to treat an allergic emergency.

Fortunately, all of these issues are lessened to a significant degree with the availability of sublingual immunotherapy, or allergy drops.

Because SLIT allergy drops can be administered by the patient or parent at home, one has good reason to believe that the compliance rate for this allergy treatment plan will be much better than allergy shots. Simply put, higher compliance means a better outcome. With sublingual allergy drops, patients simply squirt the extract under the tongue, hold it there for twenty seconds, and then swallow. This can be done anywhere; at home, on vacation, and on business trips.
And, because allergy drops have a pleasant taste, children generally do not object to this treatment. The opportunity to treat children as young as three years old with immunotherapy represents a true breakthrough in the treatment of allergies. Physicians know the importance of intervening early in the pediatric age group in order to attenuate the “allergic march”, a term which denotes the progression of allergic disease from atopic dermatitis (eczema) to allergic rhinitis and then to asthma. 

Most importantly, SLIT allergy drops are extremely safe. Minor symptoms such as itching of the mouth occasionally occur, but serious allergic reactions are extremely rare. This is very reassuring for the patient, parents, and the allergist.

Is sublingual immunotherapy something new?

Sublingual oral immunotherapy is not a new treatment modality for allergies. Allergy drops have been widely used in Europe for decades and is now gaining acceptance as an alternative to allergy shots by allergists in the U.S. and other western countries. Clinical trials are now in progress to determine the optimal dose and frequency of administration. As new scientific data emerges, it is not unreasonable to suggest that over the next ten years, SLIT may become the allergy treatment of choice worldwide among both allergists and patients.

At the present time, sublingual immunotherapy is not FDA approved, although it is recommended and prescribed “off-label”. Even though the components of SLIT extract are FDA approved to be administered by injection, they have not been approved for oral administration. Most of the efficacy and safety data about SLIT are from European studies. The FDA has requested that safety and efficacy studies be performed in the U.S. This research is well underway and, thus far, the data has suggested efficacy approximating that of allergy shot therapy and a superior safety profile when compared to allergy shots.

What can one expect from sublingual immunotherapy?

Sublingual immunotherapy is designed to desensitize one or all of the airborne allergens to which one is allergic. Like allergy shots, all relevant allergens are be included in the allergy drops such as dust mites, cat, and pollen. There is also good evidence to suggest that immunotherapy or desensitization can prevent a child who has upper respiratory allergies from developing asthma.

The response to immunotherapy is variable and depends on several factors. Approximately 80-85% of patients who are appropriately placed on either sublingual immunotherapy or injection therapy will see significant improvement over time. Most see a significant decrease in symptoms, and some fortunate individuals will have a total resolution of symptoms.

It should be kept in mind that one may not see significant improvement for 6-12 months after beginning sublingual immunotherapy. If allergy drops are effective, the therapy will be continued for 3-5 years in order to maintain improvement for many years, if not lifelong.

Who are the ideal candidates for allergy drops?

Anyone with well documented allergies can take sublingual immunotherapy, but by far, the largest segment of the population to potentially benefit from allergy drops is children. Because this treatment is totally painless, very young children with significant allergies can begin allergy drops. Children as young as three years of age can take allergy drops, therefore allowing allergists to intervene early in the allergic process.  SLIT is also ideal for older children and adults with busy school and work schedules.

What is the appropriate dose for sublingual immunotherapy?

To date, the most appropriate dose of SLIT has not been determined. This is the subject of ongoing medical research. The strength of the SLIT extract and dosing schedule will vary greatly between allergists. Like allergy shots, allergy drops are prescribed to be taken frequently at the beginning of treatment, perhaps three times a day. Over time, the frequency is gradually decreased.  Fortunately, allergy drops have a pleasant taste and compliance with frequent administration is not a problem.

What about allergy drops for food allergies?

Sublingual immunotherapy or oral desensitization to foods is one of the most exciting developments in allergy therapy. Historically, the treatment for food allergies was total avoidance of ingestion. Now, there is reason to be very optimistic about oral desensitization in children and adults with severe food allergies. Many studies have proven that orally administered immunotherapy can result in a significant degree of desensitization, or tolerance, in severely food allergic patients. Sublingual immunotherapy is not yet being offered for those with mild to moderate food allergies, and likely will not be available through your allergist for the foreseeable future. It is presently being made available only to those with life-threatening reactions to highly allergenic foods such as milk, peanuts, and tree nuts. As opposed to sublingual immunotherapy for the desensitization to inhalant allergens, SLIT therapy for food allergies is associated with a significant amount of risk and should only be performed under the watchful eye of a board certified allergist experienced in oral tolerance induction. This form of oral desensitization is being performed at a few highly acclaimed medical centers.

The availability of sublingual immunotherapy or allergy drops has made it possible for allergists to offer real and lasting allergy relief to those who suffer from allergies, allergic asthma, and severe food allergies. This highly effective and affordable treatment has the potential to greatly improve the quality of lives of many allergic children and adults.

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