It may be a sneeze which might be a sign of a respiratory infection. Is he gasping or has his crow voice changed? Infectious bronchitis, MG, and coryza are common ones. Look for any nasal drainage, eye bubbles or drainage, or swelling of the face and eyes. Antibiotics such as Terramycin, Gallimycin, and Tylan in the water are good to treat respiratory infections. Here is some reading on those diseases: http://edis.ifas.ufl.edu/ps044
