Psoriasis affects more than 3 percent of the population of America and there is a huge demand for over the counter (OTC) topical medication. The two effective ingredients approved by the FDA are salicylic acid and tar and various ointments which use them are available without the prescription of doctor.

Salicylic acid has been classified as keratolytic, a substance that has peeling effect. It helps in the shedding of the outermost layer of the skin and is not only used in treatment of psoriasis but a lot of other skin ailments. In treatment of psoriasis it acts as a softening agent that softens the scales and also removes them.

But one should be cautious of the use of salicylic acid as concentrated amounts may cause irritation if kept for a long time in contact with the skin. When treating large areas on skin, excess amount of the acid may get absorbed into the body. It can cause hair fall as the shafts weaken.

Both coal and wood tar are used to treat psoriasis but coal tar is more popular of the two. It has the ability to slow down the rapid generation of skin cells and also restore the normal appearance of the skin. It can also provide relief in itching, inflammation and scaling. Generally the higher concentration of tar in a medication has more potential than those with lower concentration.

If using tar, there are some precautions to be taken. It can stain clothes, bed and also light colored hair. So use it with caution. Moreover, it can redden and dry the skin where applied. Thus it is advised to test tar on a small patch of skin. In case of drying, it should be used over moisturizer. Tar also makes the skin sensitive to sunlight and that means it should be washed off thoroughly before going out into the sun. Still it remains active for 24 hours.

During this period one needs to be very careful about exposure to sunlight and use a good sunscreen if he or she needs to go outdoors. Those using tar regularly should also go for periodic checking for skin cancer as tar, in high concentration, can be one of the causes.

Some other OTC medications are also available and are used in treatment of psoriasis which does not use tar or salicylic acid.