Every winter my cows rub their heads, necks, and shoulders. Why do they do this?

Lice are a common cause of cattle “rubbing” in the winter time. Lice are controlled with pour-on insecticides usually applied in early to mid-winter.

Even though lice are known in the winter to cause cattle to itch and rub on objects such as fences, posts, trees, and barns, another common cause of itching and rubbing is due to an aftermath of the allergic dermatitis produced during the previous summer and fall by a horn fly infestation.

During the horn fly season, cattle quite often develop a skin allergy to the saliva of the biting horn flies. After several weeks, large quantities of hair follicles are destroyed by the inflammatory reaction in the skin. Before the damaged hair comes out during the winter, the retained hair causes an itch sensation; the cattle rub their faces, necks, and shoulders from December through March. As a result of rubbing these areas, the hair coat becomes sparse, and irritated skin lesions are evident. Once the dead hair is removed by rain and rubbing, a normal hair coat returns. In the absence of crawling lice on the skin or lice eggs glued to the hairs, diagnosis is based on a history that the cows had a horn fly infestation the previous year. To prevent recurrence of this cold-season problem, implementing measures to reduce the horn fly population is necessary in the warm seasons.