Specific allergy vaccination against seasonal allergens is used today eithe
r as a perennial therapy over three years or as a preseasonal short-term th
erapy. The allergen extracts used are composed of intact or chemically modi
fied allergens. The largest effects in placebo-controlled, double-blind cli
nical trials have been observed for the perennial allergy vaccination with
intact allergens. Lower effects have been described for the preseasonal sho
rt-term treatment with intact allergens and fur the perennial treatment wit
h chemically modified allergens. No data from placebo-controlled. double-bl
ind studies have been published fur short-term treatment with chemically mo
dified allergens so far. There is some evidence that allergy vaccination ha
s a preventive effect against asthma. As a mechanism of the efficacy a shif
t from a TH2-T helper cell cytokine profile to a TH1 cytokine profile is po
stulated. The decreased immigration of effector cells like eosinophils resu
lts in a reduced late-phase reaction.