• oral allergy syndrome;
  • SLIT

S ublingual/swallow immunotherapy (IT) (SLIT) is now accepted as a viable alternative to the subcutaneous route, and its safety has been proven in both children and adults. The most common side-effects reported are gastrointestinal complaints(especially when high doses are used) and oral itching. The safety of SLIT in patients suffering from oral allergy syndrome (OAS) still represents a major concern and a matter of debate. OAS is characterized by oral itching and swelling, edema of the tongue/lips, and peroral urticaria, which appear within minutes after contact between certain foods and the oral mucosa. OAS is frequent in subjects suffering from pollen allergy where fruits and vegetables (such as apple, carrot, kiwi, peach, and tomato) are the most common causal agents ( 1). In mite-allergic subjects, OAS is commonly due to shrimp and snail.

It has been hypothesized that in patients with OAS the sublingual administration of purified allergens may induce oral symptoms, but no study on the safety of SLIT in patients suffering from OAS is presently available.

We studied 30 patients suffering from OAS, and receiving SLIT for respiratory allergy; a matched group of 30 patients without OAS was also observed for oral side-effects, as internal control. The demographic and clinical data of the patients studied are summarized in Table 1. The diagnosis of OAS was established by clinical history, prick-by-prick, and open oral challenge with the fresh food. All patients received SLIT prepared as orosoluble tablets (LAIS, Lofarma, Milan, Italy) to be dissolved in the mouth for 1–2 min and then swallowed. The SLIT course was preseasonal for pollen allergy and continuous for mite allergy. The IT treatments were administered at the doses recommended by the manufacturer. None of the subjects were taking antihistamines or corticosteroids at the beginning and during the IT course, since they were asymptomatic. All patients had to complete a record card for side-effects at each dose taken. The presence and grade (mild, moderate, severe) of itching, burning, edema of the tongue, edema of the lips, and peroral urticaria had to be recorded.

Table 1.  Characteristics of patient population
 OAS groupNon-OAS group
Age (years) (mean SD) 24.5±622.8±5.5
Age range16–4115–34
Sex (M/F)17/1316/14
Disease (%)21 Rhinoconjunctivitis (70%) 18 Rhinoconjunctivitis (60%)
 3 Asthma (10%)2 Asthma (7%)
 6 Asthma + rhinoconjunctivitis (20%) 10 Asthma + rhinoconjunctivitis (33%)
Sensitization (%)17 Grass (57%)20 Grass (66.7%)
 9 Parietaria (30%) 5 Parietaria (20%)
 2 Mites (6.5%)4 Mites (13%)
 2 Birch (6.5%)1 Birch (0.3%)
Total SLIT courses81 Preseasonal74 Preseasonal
 5 Years continuous for mites11 Years continuous for mites
Total doses56405874
Oral side-effectsNoneNone

Twenty-eight patients with OAS suffered from pollen allergy (grasses, Parietaria, or birch), and their OAS was provoked mostly by kiwi, tomato, peach, watermelon, and cherry (also in association). The two patients with mite allergy had OAS induced by shrimp alone. The mean duration of the IT treatment in both groups was about 3 years (irrespective of the schedule). None of the patients herein observed reported oral side-effects during their multiple SLIT courses, and the treatment was optimally tolerated.

OAS is sustained by a type-I reaction and its coexistence with respiratory allergy is probably due to cross-reacting antigens or to superantigens such as prophyllins or lipid transfer proteins ( 2). A few studies (usually in birch allergy) have been conducted on the efficacy of immunotherapy in OAS patients: they studied the possible effects of the treatment on oral symptoms, and provided controversial results ( 3–5). As far as SLIT is concerned, no data are available, but the sublingual administration of purified allergens (vaccines) could be expected to elicit oral symptoms in patients with OAS. Indeed, in none of our patients did the SLIT treatment provoke oral symptoms; therefore, we can hypothesize that no cross-reacting allergen is contained in the commercial vaccine used, and that fresh food has probably a different immunologic behavior with respect to purified allergens. We conclude that the presence of OAS should not be considered a contraindication or a risk factor for SLIT, at least with pollen extracts, in patients suffering from respiratory allergy.


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  2. References
  1. SLIT seems to be safe in the oral allergy syndrome.