Chemical Peels - AHA’s - BHA’s: What are they and what do they do?

Lorraine Quinn from Beauty at the Lodge Ballybofey explains the science behind chemical peels for an easy guide on choosing the right one for you.

Though the word “acid” may sound a little frightening, dropping a little acid into your beauty regime can in fact benefit your skin. With scientific beauty terms being thrown around the industry it can get quite confusing, especially when it comes to the long list of acids contained in skincare products.

Acids are split into two categories:
alpha hydroxy acids (AHA’s) and beta hydroxy acids (BHA’s)

AHA are chemicals that slow down the natural cell turnover process by loosening the fluid that connects surface skin cells, while BHA are chemical exfoliant’s that target fine lines, pigmentation and pores. In layman’s terms AHA helps with anti-ageing, while BHA treats acneiform conditions.


How AHAs and BHAs are Different

AHAs work on skin’s surface, and are water soluble. They’re generally preferred for normal to dry, sun-damaged skin, due to their ability to enhance natural moisturizing factors within skin. They’ve also been proven effective in reducing the visible signs of sun damage.

BHA works on skin’s surface and inside the pore, it’s oil soluble, so it’s most often preferred for normal to oily skin prone to bumps, clogs, blemishes, and enlarged pores. BHA also has natural skin-calming properties, so it’s gentle enough for sensitive skin prone to redness and/or rosacea. This well-rounded, gentle ingredient is even suitable for skin prone to milia.

Acids can do a lot of things: Smooth, tighten, firm and brighten. Almost everyone can tolerate them when used as directed.

Though there are various types of acids, glycolic, lactic, mandelic, citric and salicylic acids they in fact have the most clinical research behind them and the most studies supporting their efficacy. That’s why they’re also the most commonly used acids in skin care products.

At this stage, most of us have used a product or two that contains hydroxy acids, glycolic, lactic, salicylic. We’ve heard of them, we know they work, but what exactly does each of them do?

How Hydroxy Acids Work

Hydroxy acids can do a lot of things, they can smooth, tighten, firm and brighten the skin.
What’s great is almost everyone can tolerate them in lower concentrations and will notice significant improvements in their skin when used as directed.

But how exactly do these multitaskers-in-a-bottle work? Hydroxy acids weaken the ‘cellular glue’ that makes dead skin cells stick together, encouraging exfoliation and revealing healthy, younger skin cells.

Hydroxy acids at medium to higher concentrations can also function beyond the surface of the skin and work in the epidermal and dermal layers to deliver additional results, such as collagen and elastin remodeling, pigment lightening and melanin suppression


Mandelic acid is a naturally occurring acid derived from bitter almond and wild cherry.

Mandelic acid is a highly effective acid that works on a lot of things, including fine lines, firmness, acne and discolouration. Mandelic is a slightly larger molecule, it’s better for sensitive skin types and for those with darker skin because it doesn’t trigger post-inflammatory responses or pigmentation like we see from other AHAs.

Mandelic acid is going to be one of the next big ingredients in skincare.


Salicylic acid is a naturally occurring BHA derived from willow bark (the same place we get aspirin).

Salicylic acid is both highly keratolytic and comedolytic, which means it not only dissolves dead skin cells on the surface of the skin, but it’s also able to get down into the pore, dissolve the oil and break apart the debris inside that commonly leads to acne.


A powerful age fighter, hyaluronic acid plumps and hydrates the skin by drawing moisture from the air. As we age, skin moisture can drop significantly, which makes the skin lose elasticity and expose the signs of ageing on the skin. Hyaluronic acid plays a critical role in skin health with its unique ability to hold in moisture (1000 ml of water per gram of hyaluronic acid).

Hyaluronic Acid has many benefits and is one of the most interesting ingredients in skincare


This naturally occurring sugarcane-derived AHA has long been considered by many professionals to be the best-performing AHA. As the smallest hydroxyl acid molecule, glycolic acid can penetrate the skin the deepest and the fastest.

Like all AHAs, glycolic acid exfoliates the skin by dissolving the cellular glue and exfoliating superficial, dead skin cells. Because glycolic penetrates the deepest, some studies suggest all the way into the dermis. It has been shown to be the most effective at stimulating collagen production, thus better promoting deeper wrinkle reduction.

Aside from reducing wrinkles, glycolic acid is also effective at reducing photodamage, which makes it ideal for those with more mature skin. If you have dry skin, you’ll also find glycolic particularly useful, because it draws moisture to the skin and helps prevent transepidermal water loss. It also increases the hyaluronic acid levels in the skin.

It’s important to know that because glycolic acid penetrates quickly, it can be more irritating than other AHAs and is sometimes not tolerated well by sensitive skin types.


Lactic acid is a naturally occurring acid derived from a variety of sources, most commonly sour milk. Cleopatra is believed to have bathed in it as part of her beauty rituals.

Like glycolic acid, lactic acid exfoliates as it increases moisture levels in the top layers of the skin, improving barrier function and resistance to dryness and flakiness.
Like all AHAs, lactic acid is great for general exfoliation and skin lightening. But because this is a larger molecule, it makes it somewhat “gentler” than glycolic acid.
Those with sensitive skin or darker skin often prefer lactic products over glycolic acid products because they tend to see less inflammation in the skin after use, but get similar desired results.


It is a naturally occurring acid derived from fruits, including orange, lemon and grapefruit. It is often used in skin care formulations to provide natural fragrance and preservative properties.
Citric acid is antimicrobial and often formulated into acne products for its bacteria-busting powers.

Whatever your skin type, tone or condition, there is so much research behind hydroxy acids supporting their numerous benefits. Find which ones are right for you and you will likely find yourself with happier, healthier skin!

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