br br Apart from the regular skin disease like acne, which is seen in a great number of teenagers and adults, there are still a lot of rare skin diseases. Most of these diseases are not fully characterized, and some of them even lack proper treatment. The probable cause for some of these rare skin diseases is sensitivity to allergic substances. Here is a short list of such rare skin diseases that are seen in humans. br br Scleroderma: In this, skin becomes hard and redness may be seen occasionally. However, the cause for this disease is unknown. br br Sweets syndrome or neutrophilic dermatosis: This is one of the hypersensitive reactions that are generally seen in response to allergic substances. This disease results in fever and painful plaques all over the skin. br br Urticaria: This is characterized by a wheel and flare reaction where the skin becomes red and may even be very itchy. This can also be said as an allergic reaction which develops when exposed to food materials, sunlight, water and stress. br br Xeroderma-pigmentosum: Unlike the above given allergic reactions, it is a genetic disorder. The genes involved in the normal DNA repair mechanism are altered. As a result, the damage caused by powerful UV-rays of the sunlight cannot be repaired, which manifests as redness or other symptoms over the skin. br br Goltz syndrome: It is also termed as focal dermal hypoplasia. It is characterized by presence of white lumps over the skin. These are fat filled lumps that are formed as a result of protrusion of the fat from the thin layer of the skin. Thinning of the skin and red rashes are indications of this syndrome. Other symptoms include brittle nails and fingers, deformities like presence of an extra finger or absence of a finger and underdeveloped eyes. Lungs, stomach, heart and intestines may also be affected. br br Recessive dystrophic epidermolysis bullosa: This is a very rare skin disorder in which the affected individuals cannot produce a protein that plays role in building collagen, which is responsible to keep the skin intact. As a result, the skin will be very delicate that even a slight touch or a cut results in severe blisters and sloughing off of the skin. Apart from the superficial skin covering, the body even the internal layers of mouth, intestine and esophagus may also be affected. br br Harlequin Ichthyosis: This is the reverse of the above disorder. In this case, the skin appears as a thick coat and scaly, which sheds more compared to normal individuals. Even the hair will be scaly giving the skin a resemblance close to fish.