Allergic reactions to insects may occur from saliva or injected toxins, patient sensitization to body protein of the insect, sensitization to the emanation, scale, or powder of the insect, or allergy to pollen carried by the insect. Generalized urticaria, angioedema, anaphylaxis and death may occur in sensitized persons following sting by: Hymenoptera—bees, wasps, hornets, and ants; and Diptera—mosquitoes. Eczema or urticaria may occur from contact with insects. Allergic rhinitis and asthma may result from inhalation of insects or their products. Mites are contributary factors to house dust allergy. The May and Caddis fly can cause epidemic respiratory allergy by inhalation.