In Jamaica, the slug, (Diplosolenodes occidentalis) is used in folklore practice to alleviate the symptoms of an asthmatic attack. A pure bioactive compound, glyceryl trilinolenate (GT) was isolated from the crude slug extract. Glyceryl trilinolenate is a non-toxic and specific H1 antagonist acting non-competitively to produce relaxation of tracheal smooth muscle. It also reduces cutaneous wheal formation and inflammation. This is the first scientific documentation of the actions of GT.