3. Allergen exposure/allergen-specific immunotherapy. 3.3. Allergen-specific immunotherapy.

Level of recommendation	Statement
B	Background: Some studies have examined the development of allergic sensitization to further/new allergens during the course of AIT, mostly in children with allergic rhinitis/ allergic rhinoconjunctivitis or asthma.
	Two studies were placebo-controlled and were carried out in infants with atopy or in IgE-sensitized, non-allergic children. These studies provided some indication that primary preventive AIT with house dust mite extract can prevent sensitization to other allergens in the first 2 years of life. A modifying effect on allergic symptoms could not be demonstrated.
	Statement: AIT for prevention of allergic sensitization and allergic symptoms in infants with increased atopy risk (primary prevention) cannot be recommended at the moment.
	To avoid allergic sensitization to further allergens and allergic symptoms in already sensitized, non-allergic children (secondary prevention), an AIT cannot be recommended at the moment.
	Recommendation: In patients with pre-existing allergic rhinitis/rhinoconjunctivitis, AIT to prevent a not yet manifest asthma should be recommended. (Tertiary prevention). (B)
Level of evidence	Crimi 2004 (1–); Marogna 2008 (1–); Szepfalusi 2014 (1+), Zolkipli 2015 (1++); Kristiansen 2018 (1+); Halken 2017 (1+); Jacobsen 2007 (1–); Song 2014 (1+); Valovirta 2017 (1+); Grembiale 2000 (1+)
Level of consensus:	Strong consensus