When I was younger, I spent almost every waking moment browsing skincare communities. Most posts in those communities boils down to routine help, selfies, or general questions, but sometimes, skincare routines in popular media come up. One such routine was displayed in the film American Psycho with Christian Bale. You can do a quick Google search and find numerous articles, blog posts, and videos about Patrick Bateman’s infamous daily routine and people who’ve tried to follow it.
In the film, Patrick Bateman — a man with deep, anti-social behaviors — details his morning routine:
“I live in the American Gardens Building on W. 81st Street on the 11th floor. My name is Patrick Bateman. I’m 27 years old. I believe in taking care of myself and a balanced diet and rigorous exercise routine.
“In the morning if my face is a little puffy I’ll put on an ice pack while doing stomach crunches. I can do 1000 now.
“After I remove the ice pack I use a deep pore cleanser lotion. In the shower I use a water activated gel cleanser, then a honey almond body scrub, and on the face an exfoliating gel scrub. Then I apply an herb-mint facial mask which I leave on for 10 minutes while I prepare the rest of my routine. I always use an after shave lotion with little or no alcohol, because alcohol dries your face out and makes you look older. Then moisturizer, then an anti-aging eye balm followed by a final moisturizing protective lotion.”
Showing the audience this routine reveals to us how much emphasis Bateman puts on his outwards appearance — a central theme to the film.
Most people care deeply about their appearance, whether they’re following a Bateman-esc routine or trimming their brows. After all, glowing skin is typically a sign of health.
Bateman’s routine puts particular emphasis on a youthful appearance, with multiple scrubs, peels, and moisturizers; and indeed it is exfoliation and skin-cell turnover that keeps your skin looking younger and healthier, but how do we get there from here? What should a good exfoliation routine look like? Where do you even start?
In this post, I’ll be breaking down some of the things that can keep us looking younger: AHAs, BHAs, LHAs, and azelaic acid.
Introduction to Hydroxy Acids
You may remember from my post on moisturizers that skin cells (keratinocytes) begin deep in the stratum basale — the deepest layer of the epidermis — and work their way upwards, flattening out, hardening, dying, and eventually flaking away.
However, some skin cells are not quite as good at this as others. They will build up, stick together, or get “stuck” in the pores (hair and oil gland openings) of skin. Hydroxy acids are what is called an “active” skincare ingredient — basically something that performs an action on the skin. In this case, rejuvenation and exfoliation. They are largely found in botanical sources, which is why they are frequently referred to as fruit acids, and are divided up based upon the hydroxyl groups on their molecular structures. Hydroxy acids posses the ability to separate skin cells from the stratum corneum, which can be hugely beneficial to skin diseases that are characterized by a build up of dead skin (or hyperkeratosis), such as acne. Many also have the ability to stimulate the growth of collagen in the deeper layers of the skin, resulting in the reduction of fine lines over time.
If you want to think of it in a more simple way, hydroxy acids are solutions that break down the “glue” that holds skin cells together (not the skin cells themselves), but like with anything that performs an action on the skin, this can be very irritating. Whether or not it is irritating to you depends on your needs and the formulations as well as the concentrations of the exfoliants you pick.
The term AHA is short for “Alpha Hydroxy Acid.” It is the most common of the chemical exfoliants you can find. They’re usually associated with creating glowing, youthful skin due to their ability to exfoliate away the upper layers of the stratum corneum so effectively.
They work best around a pH of 3.5, which allows for better absorption. The higher the pH, the lower the amount of acid that is absorbed by the skin. To demonstrate this, one study compared the effects of glycolic and lactic acid on the skin when applied at different pH values. At a pH of 3, the total absorption of a 5% glycolic acid cream in 24 hours was 27%. When increasing the pH value to 7, that absorption tanked to a mere 3.5%. Similarly, 5% lactic acid had a total absorption of 30% over 24 hours at a pH of 3, which dropped to 10% when the pH was boosted to a value of 7. 
They are water-soluble, meaning that they work best directly on clean, dry skin. Some even have humectant properties, allowing them to draw moisture into the upper layers of the skin.
All AHAs create photo-sensitization — or sensitivity to the sun — due to their ability to exfoliate the stratum corneum.
AHAs are also generally not recommended for rosacean or eczema-prone skin, as they can worsen the inflammation that is common in these conditions. Additionally, avoid using AHAs in combination with other forms of exfoliation (such as physical scrubbing) or prescription topicals given to you by your dermatologist, especially tretinoin/Retin-A.
There are multiple types of AHAs, and they come in various forms, differentiated by molecular size and source. The most common types of AHAs are glycolic, mandelic, and lactic.
The most common form of AHA is glycolic, and it’s found in nearly every AHA product you can find these days. It has a small molecular structure, meaning it can penetrate the upper layers of the skin more easily and quickly, but it is also the most irritating due to these properties. It’s usually found in products in concentrations of 8-10%. Some examples of popular products with glycolic acid:
Paula’s Choice 8% AHA Gel – Recommended
Water (Aqua), Glycolic Acid (alpha hydroxy acid/exfoliant), Sodium Hydroxide (pH adjuster), Chamomilla Recutita Matricaria Flower Extract (chamomile/skin-soothing), Aloe Barbadensis Leaf Juice (hydration), Camellia Oleifera Leaf Extract (green tea/antioxidant/skin-soothing), Sodium Hyaluronate (skin replenishing), Panthenol (hydration), Sodium PCA (skin replenishing), Propylene Glycol (hydration), Butylene Glycol (hydration), Hydroxyethylcellulose (texture-enhancing), Polyquaternium-10 (texture-enhancing), Phenoxyethanol (preservative), Sodium Benzoate (preservative).
Aqua, Aloe Barbadensis Leaf Juice, Hamamelis Virginiana (Witch Hazel) Leaf Extract, Aesculus Hippocastanum (Horse Chestnut) Seed Extract, Glycolic Acid, Ammonium Glycolate, Glycerin, Butylene Glycol, Hexylene Glycol (and) Fructose (and) Glucose (and) Sucrose (and) Urea (and) Dextrin (and) Alanine (and) Glutamic Acid (and) Aspartic Acid (and) Hexyl Nicotinate, Panax Ginseng Root Extract, Phenoxyethanol, Sodium Benzoate, Biotin, Polysorbate 20.
Aqua (Water), Glycerin, Glycolic Acid, Polysorbate 20, Sodium Hydroxide, PEG-12 Dimethicone, Hamamelis Virginiana (Witch Hazel) Water, Phenoxyethanol, Benzyl Alcohol, Alcohol Denat. (SD Alcohol 40-B), Disodium EDTA, Globularia Alypum (Blue Daisy) Extract, Panthenol, Lactic Acid, Parfum, Limonene, Ethylhexylglycerin, Dehydroacetic Acid, Sodium Hyaluronate, Linalool, Geraniol, Citral.
Pyrus Malus (Apple) Fruit Water, Butylene Glycol, Glycolic Acid, Niacinamide, Sodium Hydroxide, 1,2-Hexanediol, Panthenol, Sodium Hyaluronate, Xanthan Gum, Ethyl Hexanediol.
Lactic acid is the second most common of all AHAs, and can be frequently found hanging out in the ingredients with other AHAs or BHAs , though it is a fine exfoliator on its own. It has a larger molecule than glycolic, making it slower to act and less irritating — ideal for more sensitive skin. It is usually derived from milk, and has the best humectant properties out of all of the acids. Some examples of popular products with lactic acid:
Opuntia Tuna Fruit (Prickly Pear) Extract, Agave Tequilana Leaf (Blue Agave) Extract, Cypripedium Pubescens (Lady’s Slipper Orchid) Extract, Opuntia Vulgaris (Cactus) Extract, Aloe Barbadensis Leaf Extract & Saccharomyses Cerevisiae (Yeast) Extract, Lactic Acid, Caprylic/Capric Triglyceride, Butylene Glycol, Squalane, Cyclomethicone, Dimethicone, Ppg-12/Smdi Copolymer, Stearic Acid, Cetearyl Alcohol And Ceteareth20, Glyceryl Stearate And Peg-100 Stearate, Arnica Montana (Flower) Extract, Peg-75 Meadowfoam Oil, Glycyrrhiza Glabra (Licorice) Root Extract, Cymbopogon Schoenanthus (Lemongrass) Oil, Triethanolamine, Xantham Gum, Phenoxyethanol, Steareth-20, Dmdm Hydantoin.
Aqua (Water), Lactic Acid, Glycerin, Pentylene Glycol, Arginine, Potassium Citrate, Triethanolamine, Sodium Hyaluronate Crosspolymer, Tasmannia Lanceolata Fruit/Leaf Extract, Acacia Senegal Gum, Xanthan Gum, Trisodium Ethylenediamine Disuccinate, PPG-26-Buteth-26, Ethyl 2,2-Dimethylhydrocinnamal, PEG-40 Hydrogenated Castor Oil, Ethylhexylglycerin, 1,2-Hexanediol, Caprylyl Glycol.
AmLactin 12% Alpha-Hydroxy Therapy Daily Moisturizing Body Lotion – Recommended (for body)
Water, Lactic Acid, Light Mineral Oil, Glyceryl Stearate, PEG 100 Stearate, Propylene Glycol, Glycerin, Magnesium Aluminum Silicate, Laureth 4, Polyoxyl 40 Stearate, Cetyl Alcohol, Methylparaben, Propylparaben, Methylcellulose.
Mandelic acid has only just begun to appear on the scene, though it has been around for awhile. It is one of the best choices for very sensitive skin, and great for acne-prone skin due to its anti-bacterial and anti-microbial nature. It is derived from almonds and has moderate humectant properties, floating somewhere between glycolic and lactic. An example of a popular product with mandelic acid:
Stratia Skin Soft Touch AHA with 10% Mandelic Acid – Recommended
Water (Aqua), Mandelic Acid, Propylene Glycol, Polyacrylate Crosspolymer-6, Panthenol, Aloe Barbadensis Leaf Juice, Matricaria Recutita (Chamomile) Flower Extract, Glycerin, Sodium Hyaluronate, Allantoin, Sodium Hydroxide, Diazolidinyl Urea, Iodopropynyl Butylcarbamate.
There are also plenty of products that combine several alpha hydroxy acids together, such as:
Water, Glycolic Acid, Butylene Glycol, Glycerin, Sodium Hydroxide, Salicylic Acid, Lactic Acid, Citric Acid, Vitis Vinifera (Grape) Juice Extract, Aloe Barbadensis Leaf Juice, Opuntia Ficus-Indica Extract, Aesculus Hippocastanum (Horse Chestnut) Seed Extract, Camellia Sinensis Leaf Extract, Rubus Idaeus (Raspberry) Fruit Extract, Saccharomyces Cerevisiae Extract, Buddleja Davidii Meristem Cell Culture, Sclerocarya Birrea Seed Oil, Sodium Hyaluronate Crosspolymer, Allantoin, Hydroxyethylcellulose, Galactoarabinan, Propanediol, Disodium EDTA, Xanthan Gum, Hexylene Glycol, Phenoxyethanol, Caprylyl Glycol, Ethylhexylglycerin, Sodium Nitrate, Potassium Sorbate, Pentylene Glycol, Sodium Benzoate.
Water (Aqua), Alcohol Denat., Glycolic Acid, Potassium Hydroxide, Hamamelis Virginiana (Witch Hazel) Leaf Extract, Salicylic Acid, Polysorbate 20, Lactic Acid, Mandelic Acid, Malic Acid, Citric Acid, Salix Alba (Willow) Bark Extract, Menthyl Lactate, Camellia Sinensis Leaf Extract, Achillea Millefolium Extract, Chamomilla Recutita (Matricaria) Flower Extract, Soy Isoflavones, Copper PCA, Zinc PCA, Disodium EDTA, Fragrance (Parfum), Sodium Benzoate.
BHA is short for “Beta Hydroxy Acid.” These acids are slightly more complex than AHAs due to their oil-solubility. They are able to penetrate not just the skin, like AHAs, but also the pores of the skin. This is what makes them an ideal choice for acne-prones, who tend to have lipid-rich sebaceous glands.
BHAs work best around pH values of 3, and in concentrations of 1-2%. They’re frequently found with AHAs, but can be found in formulations without the addition of other hydroxy acids.
BHAs are not as photo-sensitizing as AHAs , but it is still frequently recommended that you wear a sunscreen when using any hydroxy acid.
There are two major types of BHAs: salicylic acid and lipohydroxy acid.
When discussing BHAs, the ingredient that is usually being discussed is salicylic acid, which is derived from salicin — the same stuff in asprin. Due to this origin, salicylic acid should be avoided if you have an asprin allergy.
Salicylic acid has no humectant properties, and can cause drying of the skin. Though if formulated correctly, this can largely be avoided which can make BHA a much more effective acne treatment for some than harsher, more drying topicals such as benzoyl peroxide.
It can also be soothing to some skin types, such as rosacean skin or acne skin, and is pretty well-tolerated overall.
Some examples of popular products with salicylic acid:
Paula’s Choice 2% BHA Liquid – Recommended
Water (Aqua), Methylpropanediol (hydration), Butylene Glycol (hydration), Salicylic Acid (beta hydroxy acid/exfoliant), Polysorbate 20 (stabilizer), Camellia Oleifera Leaf Extract (green tea/skin calming/antioxidant), Sodium Hydroxide (pH balancer), Tetrasodium EDTA (stabilizer).
Salicylic acid 2.0%, Ammonium lauryl sulfate, ammonium xylenesulfonate, citric acid, DMDM hydantoin, fragrance, menthol, PPG-5-Ceteth-20, purified water, simethicone, sodium borate, tetrasodium EDTA.
Lipohydroxy acid is a derivative of salicylic acid, with unique properties. It has a higher molecular weight and an added fatty chain, making it more lipophilic (oil loving) than its parent SA.
First developed by L’Oreal in the 1980s, it penetrates the skin less easily due to it’s lipophilic properties. This slower penetration means that it breaks down the glue of the skin cells slower, but it is still unclear whether or not this results in less irritation.
Like other hydroxy acids, LHA thins the stratum corneum, but has dermal thickening properties. In one study, it was shown to be as effective as tretinoin, due to it’s stimulation of structural skin proteins and lipids. 
It is excellent for acne skin due to it’s lipophilic nature, and in one study, showed a decrease of 85% in follicular plugs over 14 days. 
It is only available in products made by L’Oreal, so it is difficult to get your hands on a wide variety. Some examples:
aqua / water / eau, coco-betaine, propylene glycol, peg-120 methyl glucose dioleate, sorbitol, glycerin, glycolic acid, triethanolamine, sodium laureth sulfate, sodium chloride, disteareth-100 ipdi, phenoxyethanol, salicylic acid, capryloyl salicylic acid, menthol, methylparaben, disodium edta, steareth-100.
Water, Isostearyl Alcohol, Glycerin, Pentylene Glycol, Silica, Carbomer, Capryloyl Salicylic Acid, Potassium Hydroxide, Tocopheryl Acetate, Acrylates/c10-30 Alkyl Acrylate Crosspolymer, Disodium EDTA, Epilobium Angustioflium Flower/leaf/stem Extract.
Water / Eau, Alcohol Denat., Glycolic Acid, Sodium Hydroxide, Capryloyl Salicylic Acid, Salicylic Acid.
Azelaic acid stands on its own as an ingredient. It is derived from grains, such as barley, rye, and wheat, and has been shown to be able to kill the acne bacteria. It also decreases the production of keratin, and is typically used as a topical treatment for rosacea due to its soothing, inflammation-reducing properties.
It also reduces the production of melanin and is prescribed for the treatment of melasma and hyperpigmentation following acne. It’s particularly effective for those with darker skin tones and is frequently recommended as an alternative to hydroquinone.
It is not as irritating as AHAs or BHAs, but can make the skin feel itchy or prickly when applied.
Unfortunately, it is largely prescription-only in the US (going by the prescription name of Finacea), and can only be found in lower concentrations when purchased over the counter. Some over-the-counter examples:
Aqua, Azelaic Acid (antibacterial/antioxidant/skin-lightening agent), C12-15 Alkyl Benzoate (emollient), Caprylic/Capric Triglyceride (skin-repairing ingredient), Methyl Glucose Sesquistearate (emollient), Glycerin (skin-repairing ingredient), Cetearyl Alcohol (thickener), Glyceryl Stearate (thickener), Dimethicone (silicone slip agent), Salicylic Acid (Beta Hydroxy Acid, exfoliant), Adenoside (cell-communicating ingredient), Glycyrrhiza Glabra (Licorice) Root Extract (anti-irritant/skin-lightening agent), Boerhavia Diffusa Root Extract (antioxidant), Allantoin (anti-irritant), Bisabolol (anti-irritant), Cyclopentasiloxane (silicone slip agent), Xanthan Gum (natural thickener agent), Sclerotium Gum (natural thickener agent), Propanediol (slip agent/penetration enhancer), Butylene Glycol (slip agent/penetration enhancer), Phenoxyethanol (preservative).
Aqua (Water), Isodecyl Neopentanoate, Dimethicone, Azelaic Acid, Dimethicone/Bis-Isobutyl PPG-20 Crosspolymer, Dimethyl Isosorbide, Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer, Polysilicone-11, Isohexadecane, Tocopherol, Trisodium Ethylenediamine Disuccinate, Isoceteth-20, Polysorbate 60, Triethanolamine, Ethoxydiglycol, Phenoxyethanol, Chlorphenesin.
All Together Now
- If you’re sensitive, avoid AHA and BHA used together. Multiple hydroxy acids in one product increase your likelihood of a reaction. It’s better to start low and slow when introducing skin to a hydroxy acid.
- Lower concentrations for beginners. If you’ve never used a hydroxy acid, go for lower concentrations, such as 1% BHA (Paula’s Choice makes a 1% variety of BHA) and 4-5% glycolic acid. If your skin is sensitive and generally reactive, look for larger molecules, like lactic or mandelic acid.
- If you’re oily-skinned, rosacean, or acne-prone, try BHA. I cannot understate enough how great BHA is. It is generally soothing and can break through oils on the skin, making it ideal for acne.
- Do not use physical exfoliation like scrubs, towels, or a Clarisonic when using a chemical exfoliant. Your stratum corneum thins when using a chemical exfoliant, so you shouldn’t need to be physically scrubbing your skin, which can just create irritation.
- Use hydroxy acids infrequently. Unlike Patrick Bateman, most people do not need daily exfoliation. Use a hydroxy acid two to three times a week. Tweak this based on how your skin reacts.
- Back off if you’re breaking out. Skin irritation can occur with hydroxy acids, usually in the form of breakouts. If this occurs, discontinue use until your skin clears. Re-introduce the product slowly and use fewer days per week. If the reaction re-occurs, discontinue use entirely.
- Use a sunscreen during the day. Except for salicylic acid, hydroxy acids thin the stratum corneum and photo-sensitize the skin. You must use a sunscreen during the day to prevent damage and sunburn.
- Be careful when using BP/retinol/retinoids with AHAs/BHAs if you are very sensitive. If you’re very sensitive with conditions such as rosacea or eczema, be cautious when using other actives in addition to AHAs/BHAs. This can be too much for some skin.
- Use at night. As I said above, hydroxy acids photo-sensitize you. Use them at night for this reason.
- Use hydroxy acids as close to the skin as possible. Applying any skin “active” right after you cleanse is ideal. This ensures it is as close to the skin as possible, and does not need to penetrate any additional products to work.
- Effects of alpha-hydroxy acids on photoaged skin: a pilot clinical, histologic, and ultrastructural study.
- A review of skin ageing and its medical therapy
- Epidermal and dermal effects of topical lactic acid
- Glycolic Acid Treatment Increases Type I Collagen mRNA and Hyaluronic Acid Content of Human Skin
- Labmuffin – Why does pH matter for AHAs and BHAs
- The effects of topically applied glycolic acid and salicylic acid on ultraviolet radiation-induced erythema, DNA damage and sunburn cell formation in human skin
- The Use of Lipohydroxy Acid in Skin Care and Acne Treatment
- Comedolysis by a lipohydroxyacid formulation in acne-prone subjects.