Exfoliation – AHA and BHA

Exfoliation is perhaps the only skin care process that can improve your skin’s appearance instantly. If you choose AHA or BHA, instead of scrubs, this exfoliation process can also bring you long-term benefits. This post discusses why you need exfoliation, what are AHA and BHA, how to use AHA and BHA, side effects of AHA and BHA and what AHA and BHA exfoliation products are best for your skin type.

Why do you need exfoliation?

The skin forms and sheds a top dead layer by itself. This turn-over process happens often enough for children. As we age, the rate of skin cell renewal drops. This makes the skin look dull, rough, discolored, and more lined. The exfoliation removes the top dead layer of the skin cells and uncovers the younger-looking layer hiding beneath. If you choose well-formulated AHA or BHA exfoliants, you can also gain long-term benefits, such as skin structure improvement, skin barrier repair, and collagen stimulation.

For those who suffer from acne, exfoliation can unclog pores by keeping dead skin cells from blocking the pore opening so the oil can flow more normally, which helps reduce blemishes and blackheads.

What are AHA and BHA?

AHA stands for alpha hydroxy acid and BHA, beta hydroxy acid. In skin care products, the well researched AHA for regular use are glycolic acid and lactic acid. The BHA ingredients are salicylic acid and its lipophilic derivatives (still listed as some kind of salicylic acid).

The exfoliation benefits of AHA are highly dependent on concentrations and pH. The most effective pH range at different AHA concentrations is sorted in the table below.

Group A: effective but more acid than most retail.
Group B: good evidence efficacy.

AHA Concentrations
10% 8% 4%
Group A 3.5-3.9 3.5-3.6 none
Group B 4.0-4.4 3.7-4.2 2.0-4.0

The exfoliation benefits of BHA do not seem to be as dependent on the concentrations and pH. Because of its potential for irritation at higher concentrations, salicylic acid is mostly used at concentrations of 1.5% or less in over-the-counter products. The recommended pH is around 3. But it is also reported that even neutralized salicylic acid has certain exfoliation benefits[1] although it is less effective than the low pH products. Nevertheless, this information will benefit those that feel too irritated by the regular low pH AHA or BHA products.

Generally, at the concentrations and pH of over-the-count products, AHA exfoliation products increase the skin renewal rate more than BHA exfoliation products. Also, BHA tends to be less irritating. From my own experience, over-the-count BHA is not effective enough as an exfoliant. That is why some of the consumers need products with both AHA and BHA as listed at the end of this post.

How to use AHA and BHA?

The frequency of exfoliation varies among different people. It can be once or twice a day, every other day, or twice a week. I wish there were a clear rule for this but, in fact, you have to find the most suitable frequency yourself. You can start from twice a week and finally you want to find a frequency that will maintain a smooth looking of your skin but doesn’t turn your skin red.

You can use both AHA and BHA but I suggest you not to use one on top of the other at the same time. Using two exfoliants together can alter the concentration and pH of each product. So if you do decide to try both, you can either use products formulated to have both (products of this type are recommended at the end of this post) or use AHA and BHA alternatively.

You can either use AHA or BHA for night time or day time as long as you protect yourself with sufficient sunscreen during the day.

It is extremely important to use sunscreens with both UVA and UVB protection (as discussed in Do You Use Sunscreen Correctly?). Exfoliation makes your skin more similar to children skin, which is more vulnerable to sun light.

Side effects of AHA and BHA

AHA and BHA can slightly increase the sun sensitivity of the skin. This can be compensated by the use of a well formulated sunscreen with both UVA and UVB protections.

AHA and BHA only exfoliate away dead or damaged layer of the skin so they pose minimal risk of hurting the healthy skin cells. From my experience, however, over exfoliation can still occur with AHA or BHA. Just watch your skin. If it turns red and hurts, then you have over exfoliated.

When you just start using AHA or BHA, your skin might experience some level of tingling or stinging sensation. This is normal. Generally, tingling from AHA or BHA is sensory irritation. It is believed that there are no clinical signs of irritation at the level of the concentrations and pH of over-the-counter AHA or BHA products[2].

Of course, if you keep having symptoms such as redness, flaking, or patches of dermatitis, reduce the frequency of exfoliation immediately. If it continues for more than two weeks, stop using it.

If you really cannot tolerate AHA

Switch to PHA (polyhydroxy acids or polyhyroxy bionic acids) products. Most people can tolerate PHA. Find more information about PHA in Exfoliation – PHA.

What AHA and BHA products are best for your skin type?

I picked the following AHA and BHA products because they do not only have the correct concentrations and pH but they also contain no or minimal irritating ingredients. Some of them also have other beneficial ingredients. I mention other beneficial ingredients only if their concentrations are enough to make a difference.

Please note that the skin types I marked are not absolute. For example, you have dry skin and have established your skin care regimen. Now you want to use an AHA exfoliation product under your favorite moisturizer. Then you might want a lightweight AHA exfoliation product because you don’t want to put one emollient product on top of the other.

Generally, an exfoliant is “stronger” when the concentration of AHA or BHA is higher and/or the pH is lower, and “milder” otherwise. So make a choice based on your need.

[1] Merinville, E., Laloeuf, A., Moran, G., Jalby, O., Rawlings, A. V. Exfoliation for sensitive skin with neutralized salicylic acid? International Journal of Cosmetic Science; Jun2009, Vol. 31 Issue 3, p243-244, 2p.
[2] Skin Moisturization.

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