Total serum tryptase levels are higher in young infants.

Background: Mast cells participate in immune defense and allergic disease. At baseline, serum tryptase levels primarily reflect mast cell burden, while mast cell degranulation leads to granule tryptase release, which may be detectable as a transitory elevation of serum tryptase levels. Thus, mast cell burden and mast cell activity are reflected by serum tryptase levels, but reports are scarce in infants under 1 yr.