Immunotherapy was first reported in 1911 and involved repeated injections with allergens to induce tolerance. Each allergen to which a person is sensitive must be treated except for instances of  cross-reactivity where one antigen is similar enough in structure to another to elicit tolerance for that antigen. Minor modifications to the technique of subcutanceous immunotherapy (SCIT) have been made over the years, but this form of therapy has been dominate in the United States for a century.

 

Unfortunately, SCIT is not without risks and disadvantages. Years of weekly injections can become inconvenient  and adverse effects include local skin reactions with itching, shortness or breath, and even shock. Very rarely death has been reported, usually in asthmatics. Current recommendations include a 20 minute observation following injections given only in a physician's office.  Given these limitations with SCIT, investigators have developed alternative forms of immunotherapy with increased safety, convenience, and compliance.

 

As early as 1913, alternative techniques were proposed, with nasal and oral immunotherapies showing the greatest promise over the years. Oral therapy includes the direct swallow and the sublingual (under the tongue) methods (SLIT).   In 1998 the World Health Organization approved both the sublingual and nasal methods as viable alternatives to SCIT.  Nasal delivery of immunotherapy has proven to be difficult and less accepted than oral methods. Oral immunotherapy with immediate swallowing is less effective than SLIT in most studies. 

 

Immunotherapy by any method has been thought to work primarily through three mechanisms 1) antibody action  (blocking antibodies) 2)  inflammatory chemicals and 3)cellular inflammatory responses (White blood cells). It appears that SLIT may use different mechanisms of action than those of SCIT.  

 

It appears that the effectiveness of SLIT may relate to the duration of contact with the mouth’s lining. There may be a critical interaction between the immune cells of the floor of the mouth and this effectiveness. Studies show minimal absorption, but persistence of antigen in this area for long periods.   Antigen that is swallowed is minimally absorbed and essentially completely degraded in the upper intestine, but there may be some minimal effect in the esophagus lining. It is very important to watch the clock when taking a dose of SLIT to ensure a 2 minute exposure time in the floor of mouth before spitting or swallowing the antigen.

 

The effectiveness of SLIT has been based on patient reports of symptom decrease and reduced dependency on medications.    Treatment duration of at least two years appears critical for most antigens. Pollen immunotherapy appears to be most effective with dust mite and pet epidermals possibly requiring longer durations of treatment. We believe effects are seen in about six months in most cases.

 

There have been only mild reactions noted such as oral itching, headache, runny nose, hives, constipation or other gastrointerstinal side effects. To date there have been three episodes of anaphylaxis associated with SLIT. Two of these were with food allergy SLIT and one with Latex SLIT. No reports have been with inhalant allergens. There have been no reported deaths. 

 

We follow the American Academy of Otolaryngic Allergy dosing.recommendations whereby all patients are started at a standard concentration and advanced over twelve weeks to the maximum strength dosage.  This is continued daily for one year. If  no response is seen by a year, therapy is stopped. For patients responding to therapy, it  is continued for 3-5 years before trying to terminate.  After 5 years a small percentage of patients will not develop lasting tolerance and may require longer therapy.

 

 

In 2005, the Asthma and Allergy Foundation of America performed a survey of allergy patients that asked for the important features of an allergy medication.  These were the features that were important to 50% or more of the respondants, and how these features relate to SLIT.

 

 

1.  Long lasting symptom relief               Immunotherapy is the only

                                                                       lasting allergy treatment

 

 

 

2.  Rapid relief of symptoms                    Generally 6 months to see effects

 

 

 

3.  Minimal side effects                             Appears safer than SLIT in terms

                                                                       than anaphylaxis

                                                                       Rare tingling in mouth

 

 

 

4.  No sedation/drowsiness                     None

 

 

 

5.  Covered by insurance                          No, but cost may be 

                                                                       comparable with insurance

                                                                       copays

 

 

6.  Inexpensive                                            Indirect cost savings

                                                                    

7. Safe with other medications                Yes, except for "Beta Blockers"

 

 

 

8.  Easy to take                                            Home based, once a day,

                                                                       self-administered

 

 

 

9.  Non-habit forming                                 Not addictive, but should be

                                                                       a habit

 

 

 

10.  Dosing flexible (as needed)             Best if used regularly

 

 

 

11.  Targets specific symptoms              Reduces all symptoms of allergy

 

 

 

12.  Steroid-free                                          Yes