Sublingual versus injective immunotherapy in grass pollen allergic patients: a double blind (double dummy) study

Injective immunotherapy is a well-known and recognized treatment for allergic diseases, but its safety has been questioned during recent years. Alternative administration routes have been proposed and there is a growing interest and experience in sublingual therapy. The safety of alternative routes is nonetheless a real advantage, so long as it is not counterbalanced by a loss of clinical benefit.

We have compared the efficacy of the same biologically standardized grass pollen extract administered through the injective or the sublingual route, in a group of 20 patients followed for two pollen seasons.

Both therapies were administered for 12 months according to a double-blind (double-dummy) plan; at the end of the trial the cumulative dosage of the sublingual therapy was 2.4 times higher than that of the injective therapy. Data about skin reactivity, symptoms and drugs scores during the pollen season, as well as total specific IgG and specific IgG4, during and after the trial, were obtained.

Our data show that sublingual and injective therapy are equally effective according to subjective clinical parameters, with a statistically highly significant reduction of symptoms and drugs (P = 0.002 for symptoms and drugs in SLIT-treated patients; P = 0.002 for symptoms and P = 0.0039 for drugs in patients given injections). On the other hand, objective parameters (total specific IgG, specific IgG4, skin reactivity) changed only in patients treated with active injective therapy, with P < 0.001, P < 0.001 and P = 0.021, respectively.

The discrepancies observed could be interpreted as a consequence of different mechanisms of actin of the two therapies or to the lack of close relationships between the clinical and the objective parameters which were considered here.