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Hydroxy Acids: Type, Uses and Benefits
Recently, I talked to you about exfoliation. Exfoliation is done to eliminate dead cells from your skin. After exfoliation, the skin looks luminous, smooth, younger, hyperpigmentation areas can be reduced and can help skin with acne. While choosing the exfoliator, we need to be very careful, as we should not damage the skin while doing. Physical exfoliators can be very aggressive and sometimes it is better to choose a chemical exfoliator,
Hydroxy acids are the main type of chemical exfoliators. Hydroxy acids are organic acids obtained from plants or fruits. Used in the right way, they can be beneficial for skin and delay signs of ageing.
Though the term acid can be scary, these types of acids are not dangerous if used in the right way and they are very important to keep healthy skin. They have been used from ancient times. Cleopatra, the Egyptian queen, was famous for her milk baths to keep skin healthy. Nowadays we know that lactic acid contained in milk has lots of benefits for the skin.
Different type of hydroxy acids
Chemically, these molecules are carboxylic acids containing a hydroxyl group. Depending on the position of the hydroxyl group in the carbon chain, the hydroxy acids are classified in alpha-hydroxy acids or AHA ( OH in Cα, first carbon atom after the carbonyl group), beta-hydroxy acids or BHA (OH in Cβ, second carbon atom after the carbonyl group) and poly-hydroxy acids or PHA (similar to AHA but with a bigger size).
Alpha-hydroxy acids (AHA)
AHAs are soluble in water and they act breaking the links between dead cells with a new skin to help to eliminate it. They make their job in the outer layers of the skin and they don’t penetrate into the pores.
They improve skin tone and reduce fine lines and wrinkles appearance. They help with hyperpigmentation problems and illuminate the skin. As they are hydrosoluble, they present humectant properties. The AHAs are ideal to keep dry skin hydrated as they reduce the loss of water.
Example of AHAs are glycolic, lactic or mandelic acid among others. Glycolic acid is the smallest AHA and penetrates the skin easily. Lactic acid has a double function, as it is also used to regulate pH in some products.
Beta-hydroxy acids (BHA)
BHAs are liposoluble, that means, soluble in oily substances. BHAs dissolves in the face oil and penetrate the pores, helping to keep them clean. They are indicated for oily and acne-prone skin types.
The most common BHA is salicylic acid. If you are allergic to aspirin make a patch test before applying BHAs.
Poly-hydroxy acids (PHA)
They are very big molecules and that makes them produce a milder action, reason why they are indicated for sensitive skin or to get introduced in the use of hydroxy acids. They are very mild exfoliators and can be used for sensitive skin type.
An example of PHA is the compound called gluconolactone. It is a naturally occurring polyhydroxy acid (PHA) with moisturizing and antioxidant activity. Chemically, it is a cyclic ester of D-gluconic acid, the delta-lactone of gluconic acid.
Benefits of hydroxy acids
First and most important, they are exfoliators. Basically, what hydroxy acids do is to eliminate dead cells from the external layer of your skin. That is a natural process occurring in our body but with the age, the process becomes slower, dead cells accumulate on the skin giving an irregular texture to our complexion. With hydroxy acids, your skin becomes smoother and small lines and wrinkles are less visible.
The consequence of that exfoliation is that other actives in the formulation will have more efficiency as they act over new skin. For example, if the product has AHA and hyaluronic acid, the latest will penetrate deeper on your skin compared with hyaluronic acid on his own.
Hydroxy acids have also a very good effect in reducing hyperpigmentation and scars or acne marks, mainly for the same reason, the are exfoliator, eliminate dead cells and promote cell renewal.
How to use the Hydroxy Acids
Be extremely careful when using hydroxy acids and do not forget they are acids. Always make a patch test before applying on your face.
You can find a different hydroxy acid concentration. It is always better to start with a low concentration and once your skin is used to them you can increase concentration.
Apply hydroxy acids after washing your skin thoroughly and my advice is that it is better to use them as part of the night routine. Never apply them over damaged skin or around your eyes area.
The most popular hydroxy acids are azelaic, glycolic, lactic, mandelic and salicylic. Each one has different effects on your skin. I will be doing a series of post about each one of the next year.
Six things you should know about hydroxy acids
1. Which acid shall I choose?
Think about which are the effects you want to achieve and how sensitive your skin is.. It is a good choice to start with PHA or BHA and if your skin is fine after some time, you can move on to stronger AHA.
2. Which type of product shall I use?
If you have never used them, you can start using a cleanser containing hydroxiacids as NIP+FAB Salicylic Acid Salicylic Fix Gel Cleanser or with a toner like THE ORDINARY Glycolic Acid 7% Toning Solution. If your skin feels comfortable you can then move to a serum or hydroxiacid solution as the solutions of The Ordinary and The Inkey List.
3. How to use them?
Apply onto your cleanse face evenly avoiding eye area and leave them sit for at least 5 minutes. After that time you can apply your moisturizer or other products. Don’t apply a second acid containing product.
4. When should I apply them?
It is better to apply them in the night as they can produce damage on your skin when exposed to sun radiation. Anyway, apply sun protector in the morning, even in winter.
5. How often shall I apply them?
It is better to start using them once or twice a week and slowly increase the frequence.
6. How can I include them?
Start using only one, once or twice a week. During the first month, increase frequence of use. If all is fine, during the second monthyou can increase concentration. After this time, your skin should be used to hydroxiacids and you can use one every night and once a week make a deeper exfoliation with a more concentrate AHA, as for example, the well-jknow The Ordinary AHA 30% + BHA 2% Peeling Solution.
Most Common Hydroxiacids for Skincare
Glycolic Acid. It comes from sugar cane and it is very irritant. It is a very small molecule and penetrates deeply in the skin.
Lactic Acid. It is produced in milk fermentation. It is milder than glycolic acid and it is indicated to reduce hyperpigmentation.
Mandelic Acid. It is coming from almonds.
Citric Acid. It is a hydroxy acid but its main use is as pH regulator. It is also antioxidant and it is used as an additive.
Tartaric Acid. It is coming from grapes. It is rich in antioxidants and it is a good humectant.
Salicylic Acid. It is a BHA obtained from birch or willow bark. In a 2% concentration, it is recommended for acne-prone skin.
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Hydroxy acids are very good ingredients to have a smooth, youth skin, and because of the variety of hydroxy acids existing, it is very easy to customise the use to your needs. However, they are acids and you should be very careful when introducing in your routine. Do that slow and if there are signs of irritation stop using immediately. I am nor dermatologist or medical doctor, I am a doctor in chemistry, and I learnt about the use by my own experience. In case of doubt, consult your doctor or pharmacist.