Diseases can be caused or fostered by hereditary tendency and/or the keeping conditions of the animals. With reference to natural features on leather especially two kinds of diseases are to be named: calf lichens and the occurrence of warts.
Calf lichens infest in particular young animals. It is caused by a fungus and transferred by spores. The infested calf and young cattle mainly show round, hairless areas which are covered with crusty scab on the head and in the neck area. The skin underneath the scab can substantially change its structure even if the infestation is cured.
Warts also change the skin structure. Cattle have also to deal with these little new formations of the skin that are caused by viruses. The point-shaped changes of skin are visible in naturalness-maintained leather.