In the presence of certain chemicals in the bloodstream, sunlight can cause reactions in the tissues themselves. This can vary from very mild to very severe reactions, even death. Lightly pigmented (white) areas of skin are more susceptible to damage from sunlight. The most common cause is some element or toxin from plant material (weeds, etc). Alfalfa has been known to cause this problem in some animals. Also implicated are drugs such as phenothiazine, sulfas, and tetracyclines. Some medications (especially pour-on preparations) given to mothers can cause nursing offspring to show damage to white areas, especially on the ears, in the presence of sunlight, implying that the offending substance has been transferred through the milk.
Symptoms will appear on the white parts of the body such as head, ears, eyelids, face, lips, neck shortly after exposure and may include redness, swelling, scabs, and even necrosis (the tissue dies). If there is involvement of the liver, icterus (yellowing of the eyes and skin) may be present.
Lock inside during the day and let them out at night to graze. Eliminate the causative agent if it can be identified. Prevent secondary infections and flies. Topical antibiotic creams can be applied to affected areas.
It is impossible to tell which animals will react in this manner. If it happens always make a note of it so that the problem is not repeated in the future. Always read drug labels carefully and be VERY cautious about giving any medication to any animals under one month of age.
Once again, goats are not as susceptible to this problem as are cattle (especially Hereford) and sheep.