Two patients who suffered from allergic rhinitis, conjunctivitis and contact urticaria caused by the two-spotted spider mite (Tetranychus urticae, Koch) are described. Both patients worked in a greenhouse where they came in contact with both spider mites and predator mites living on bean leaves. Prick, Prausnitz-Küstner and RAST tests indicated type I allergy to spider mite but not to predator mite. Both patients had a high level (RAST score 4) of spider-mitE-specific IgE in their sera. Radioallergosorbent test (RAST) inhibition studies revealed no cross-reactivity between spider mite and house dust mite allergens.
These results show that spider mites, which are herbivorous mites found in nature, in greenhouses and even in homes, can cause IgE-mediated allergy in man.