Dander on dog (poodle) hair, coloured scanning electron micrograph (SEM). Dog and cats produce human allergens. Pet dander is the material shed from the body of various animals (commonly cats and dogs). It may contain scales of dried skin and hair. Substances within the dander can cause human allergies (allergic reaction). An allergic reaction is a histamine reaction that is usually characterized by coughing, wheezing, itching, nasal congestion, rash, watering eyes, and sneezing. Magnification: x160 when shortest axis printed at 25 millimetres.