Hydroxy-acids are active substances , exfoliants, that if properly used can be  beneficial for the skin.Skin regeneration constantly happens and dead cells from the epidermis are eliminated. New healthy cells appear. Hydroxy-acids help to make this process faster. Hydroxy-acids belong to the chemical exfoliation of the skin.

Types of hydroxy-acids

Alpha Hydroxy Acids (AHAs) are water-soluble acids of different molecular weight. The lower the molecular weight is, the more the acids penetrate the skin. AHA peels have been popular for many years in dermatological practice.

Most common AHA is Glycolic Acid. It is the smallest size molecule and has  therefore better skin penetration. It can be extracted from sugarcane, beets, cantaloupe, pineapple and grapes.It can be found in many skincare products such as cleansers, toners, essences, serums even in shampoos. It is used for its antiaging properties, acts against acne, unclogs pores, reduces hyperpigmentation giving the skin a more even tone and significantly helps to reverse sun damage. May also enhance collagen production.

Lactic acid, is a a larger molecule than glycolic acid and it is therefore  gentler and a better option for sensitive skin. Naturally found in milk and certain fruits. It is at the same time an exfoliant and a moisturizer. Removes dead cells, treats hyperpigmentation, lighten dark spots, improves skin texture and gives a more even tone to the skin.  If you feel that your skin can’t tolerate Glycolic Acid, this one can be a good alternative. Must also be used in moderation.

Mandelic acid, naturally found in bitter almonds, acts as the previous two, it is gentler and suitable for very sensitive skin.

Malic acid found in certain fruits and wine, is a humectant and an AHA.  It has a mild action and it is used with AHA’s in skincare formulas.

Citric acid, mild exfoliator, helps to smooth and brighten the skin as well as to adjust the pH of products.

Although hydroxy-acids are beneficial to the skin, they may have some downsides when they are improperly used or overused. Especially the glycolic acid. Possible side effects could be: irritation, burning, skin rash, intense peeling, chemical burns, especially if used in high concentrations.

It is always recommended to have a patch test then start with lower concentration, avoid overuse as well as being careful with other cosmetics that are also applied to the skin. It often happens that acids are part of their ingredients list. It shouldn’t be used on skin with sunburns, very dry or already irritated skin. Preferably used at night and sunscreen is required in the morning. Remember, your skin after exfoliation is sensitive to sunlight. Always follow the instructions of use by the cosmetic brand and don’t listen to what is probably said on social media. We are talking about your skin.  Even if it is a toner and the brand recommends daily use, avoid doing that if you are a beginner. This is the best way to help your skin adjust to the substance. Besides, your skin doesn’t need exfoliation all the time.

If you decide to pass from a lower concentration to a higher, the process is the same. If you notice any adverse reactions, discontinue the use and let your skin “calm down” by moisturizing and nourishing or even using a regenerating cream.

Beta Hydroxy Acids (BHAs) contrary to AHA are liposoluble, eliminate dead cells, penetrate the skin and unclog the pores.  It is a better option for oily or acne-prone skin. Could also be used to clean the skin from blackheads or whiteheads because of their ability to deeply penetrate the pores.

Salicylic acid is the most common BHA. During the first days of use may cause irritation, redness, dryness. The skin may be very sensitive. Its use should be gradually increased. Again, if you feel uncomfortable with it, don’t use it. Apparently, it is not the right active substance for your type of skin.

Polyhydroxy acids (PHAs)  are water-soluble, have higher molecular weight which makes them to act on the surface. As a result, they are less irritating because the exfoliation is gentler. Most common PHA are gluconolactone (gluconic acid), lactobionic acid, zinc gluconate and galactose. In the long term, they may have anti-aging effects but less than the more powerful AHA’s.

Precautions

You can possibly use hydroxy acids with niacinamide as long as you don’t apply one after the other. If you do so, the pH of the acids will increase and the niacinamide’s will decrease. Τhis will reduce their efficacy.However, I have noticed the combo in some cosmetic products which means that the brand stabilized the formula.

Hydroxy-acids and retinoids could harm your skin barrier if you use them in the same routine. Instead of trying to find the appropriate way of introducing them, I would suggest to choose one of them. You don’t need to overload your skin with active substances that potentially will damage your skin barrier.

Avoid using hydroxy-acids with vitamin C. Your skin will be irritated.

Don’t use hydroxy-acids with peptides. Peptides will be less effective.

Always use a broad spectrum sunscreen SPF50.

Apply the hydroxy-acid on a dry skin.

You should also avoid to use different exfoliants at the same time.

Generally speaking, the night you use hydroxy-acids only moisturize and nourish your skin. Next morning you can use the other active ingredients unless your skin is irritated. Then, avoid to apply vitamin C. I would even suggest not to apply Vitamin C next morning if you feel your skin dehydrated. It depends on your skin. You know better than anyone else. You don’t have to follow the trends that can cause damage to your skin barrier.