Photosensitization in Dogs

This is a medical condition where the skin develops extreme sensitivity to sunlight. Photosensitization should not be confused with sunburn. There are particular molecules in the skin that gain their energy from sunlight. As the molecules revert to a less energized condition, the energy that has been released leads to chemical reactions in the skin.

The classification of photosensitization is usually dependent on the origin of the photodynamic pigment. There are two kinds of photosensitivity that affect dogs; primary (type I) and secondary (type III). Bacteria, plants, and fungi contain a large variety of chemicals that can act as photosensitization agents. Liver damage that has resulted from any type of poisoning can also bring about photosensitisation.

All the signs related to photosensitivity are alike, in spite of what the cause may be. Dogs suffering from the condition tend to fidget in visible uneasiness when exposed to light. They rub or scratch areas of the skin that are exposed (muzzle, ears or eyelids) or lightly pigmented. Even animals with black coats of hair can undergo photosensitive skin changes from bright sunlight. The initial signs include rapid development of redness and followed by swelling. The skin defects quickly resolve if the exposure to light ceases at this stage. However, if there is continual exposure, the result would be scab formation, fluid discharge, and skin death.

In cases of clear photosensitivity, the signs are easy to identify, though they tend to resemble the early or mild effects of sunburn. Your veterinarian will examine skin and check for any signs of underlying diseases. It may be essential to assess the liver enzymes and perform liver biopsies in order to establish if your dog has liver disease. Laboratory tests might also be conducted. In addition, your veterinarian will enquire whether your dog has any access to poisons, or if your dog might have been exposed to rat poison or other toxic chemicals.

Most treatment involves easing the signs. As long as the animal remains photosensitive, it should be kept in shaded areas, preferably indoors, or let out only at night. The extreme trauma of photosensitization and widespread damage of skin tissue can lead to grave illness and even death. It may be helpful to administer steroid injections, depending on the individual situation. Fluid discharge and secondary skin infections are dealt with using regular wound management methods. Flies must be kept away from the affected animal as the damaged skin attracts flies and could result in secondary diseases and maggot infestation. Skin defects due to photosensitivity heal surprisingly well, even following extensive damage. The final outcome for a dog is influenced by the degree of healing, location and severity of the initial lesion and/or liver disease.

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