Salicylic acid is a beta hydroxyl acid, derived from the bark of the willow tree, that has a wide variety of uses related to skin care. Beta hydroxyl acids are better at treating surface skin conditions than their alpha hydroxyl acid relations, as they have larger molecules which do not penetrate the layers of skin so easily. Because alpha hydroxyl acids pass deep into the skin, they can cause further irritation, making skin conditions worse.

The main use of salicylic acid is to reduce the symptoms of mild acne. Acne is caused by excess oil production and skin cells shedding in hair follicles. This blocks the follicle and provides a place for bacteria to grow, resulting in inflammation and a pimple. This over-the-counter treatment works by slowing down the rate at which the skin cells shed, and breaks down the material that creates the spot.

You can combine salicylic acid with a variety of other substances to increase its' acne fighting properties; one good example is retinol. However, you should not combine this acid with sulfur, benzoyl peroxide or resorcinol as this will be too irritating for the skin. It will stimulate oil production, making your condition worse.

You will often find salicylic acid used in chemical peels used to reduce the appearance of mild acne scarring, and to generally purify the skin. The concentration of this acid will have an impact on the effectiveness of the peel. Up to 20% can be used, but this may cause extensive skin peeling for around three days, and may be too strong to be used in weekly peels.

Salicylic acid can be used as a remedy for various other skin conditions. It is often an active ingredient in anti-dandruff shampoos, and is used to treat skin disorders such as psoriasis. It also has collagen boosting properties that make it ideal for slowing the development of wrinkles.

Applying this topical treatment in gel form to warts and verrucas has two benefits. Firstly it softens the layers of skin that make up the wart, enabling removal with a pumice stone. Secondly it irritates the wart or verucca, which stimulates the immune system to fight harder to get rid of it.

So what are the negative effects of salicylic acid? The first you may have heard about - it can cause birth defects when taken by pregnant women. The truth is that women would need to take large doses of this acid orally for their baby to be in any danger. Even so, it is advisable for pregnant women to avoid using it, as it does penetrate the skin and enter the blood stream to some degree. Another potential side effect of salicylic acid is that it can cause hyper-pigmentation, when used in high concentrations on darker skin.

Overall it is a fairly safe and cheap way to treat mild skin complaints. As a rule you should always start with a low concentration of the acid, and build up if it is not having the desired effect. You should also ensure that it only comes into contact with affected skin and not healthy skin when used in higher concentrations.

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If you'd like to learn more about over-the-counter acne products, click here. Rebecca discusses different acne treatments and their effects.