Boots Tea Tree & Witch Hazel Exfoliating Face Scrub

Isohexadecane is often used in products designed to help oily skin. It is lightweight and non-greasy while helping to moisturize. When mixed with silicones, it gives a product a silky feel.

As an occlusive, it forms a protective layer on the skin that locks in moisture and prevents transepidermal water loss (TEWL). This makes it especially great for compromised skin barriers.

The "it clogs your pores" myth has been around for decades; a study found that industrial-grade mineral oil may be comedogenic but cosmetic-grade mineral oil is not (these two are very, very different).

A 2017 review concluded that cosmetic use of mineral oils and waxes does not present a risk to consumers due to absorption.

Mineral oil got a bad rap from the old rabbit ear studies. When tested on actual human skin, cosmetic-grade mineral oil showed no comedogenic activity. The rating of 0 is a correction of outdated science.

Mineral oil is an inert substance with no fatty acids so there's nothing to feed Malassezia. This ingredient is fungal acne safe.

Your skin makes glycerin on its own (mostly from sebaceous oil breakdown) and shuttles it to your outermost layer of skin, or your epidermis, via aquaporin-3.

Aquaporin-3 is a transporter that is essential for normal skin hydration, elasticity, and repair. Interestingly, mice lacking in AQP3 have dry and less elastic skin that can be fully corrected with glycerin.

This ingredient is non-irritating, plays well with almost every ingredient, and works across all skin types. Typical use is anywhere between 3-10% but can go up to 79% in some leave-on products.

Just know very high concentrations (>40%) can feel tacky in low humidity.

Glycerin is the name for this ingredient in American English. British English uses Glycerol/Glycerine.

Silica is often used for absorption and can help reduce shine when products are applied.

You'll most likely see it paired with steareth-2 because the two work together to create stable formulations.

1,4-dioxane is often brought up as a concern but this is usually removed through purification.

It plays several roles in a formula:

Typical use levels for this ingredient sit around 1-10% and the Cosmetic Ingredient Review Expert Panel has affirmed safety at concentrations up to 25% in leave-on products.

Multiple assessments have found it to be non-irritating and non-sensitizing to most people.

However, there have been some cases of allergic contact dermatitis in patients with chronically compromised skin barriers.

Cetearyl alcohol has a comedogenic rating of 2 and irritancy rating of 1. Both of these numbers come from the 1989 study that used rabbit ears; a "2" means mildly comedogenic and a "1" means low irritancy.

Here's the catch: rabbit skin is more sensitive than human skin and throws a lot of false positives. A 1996 reappraisal found that ingredients rated 1-2 in the rabbit ear tests are generally safe for humans.

Remember comedogenic ratings are unable to assess the entire formula of a product or how it will react on your skin. Just be sure to patch test if you are unsure about certain ingredients.

This ingredient is not fungal acne safe. Cetearyl alcohol is a fatty alcohol with chain lengths that fall within the range that Malassezia can metabolize.

A 2019 study has also observed Malassezia growth in the presence of this ingredient, confirming it to be not-fungal acne safe.

Is it bad for your skin?

The answer comes down to concentration. Patch and wash studies have found highly concentrated alcohol-based hand rubs (60-100%) cause less barrier disruption than washing with a basic detergent like SLS. The only measurable effect in these studies was a temporary dip in skin hydration.

Concentrations below 12-15% in leave-on cosmetics is generally well-tolerated. Concentrations above start to see increased transepidermal water loss (TEWL) and reduced hydration.

In concentrations about 58%, it creates temporary channels in your skin's lipid layers to become more permeable and allow other ingredients to slip through easily.

This ingredient can be up to 80% of the formula in alcohol-based perfumes.

Overall, this ingredient is probably harmless if found lower down an ingredients list but worth side-eyeing if it's high up (especially if your barrier is already struggling).

Alcohol can worsen dry skin, eczema, and oily skin, especially at higher concentrations. This is because it can increase transepidermal water loss and decrease hydration to disrupt the skin barrier.

According to the National Rosacea Society based in the US, you should be mindful of products with these alcohols in the top half of ingredients.

True allergic contact dermatitis to ethanol is uncommon, but be sure to patch test if you have dry or sensitive skin.

In testing, this ingredient was nontoxic in acute oral studies and not a skin irritant or sensitizer.

You might hear concerns about 1,4-dioxane as a byproduct of ethoxylation; this is well-known in the industry and is controlled through purification steps before the ingredient is blended into finished products.

A high amount of carbomer can cause pilling or balling up of products. Don't worry, most products contain 1% or less of carbomer.

This is also one of the most heavily studied preservatives out there and major regulatory bodies have repeatedly given it the green light.

In 2023, the EU's Scientific Committee on Consumer Safety (SCCS) confirmed that this ingredient is safe up to 0.4% on its own, of up to 0.8% when mixed with other paraben esters.

Here's the science behind the noise behind parabens/hormones as well:

Methylparaben shows very weak estrogen-like activity in vitro tests (more than 1,000x weaker than your body's own estradiol). In vivo (live-organism) studies don't support a meaningful endocrine-disrupting effect either.

You get a stronger estrogenic effect from eating tofu, actually.

It's also a low sensitizer and allergic reactions are uncommon; they usually happen on damage or broken skin.

There is a caveat: France has proposed to formally re-examine its endocrine classification in 2025 so the regulatory conversation isn't fully closed as of yet.

But as it stands today, this ingredient is considered safe at permitted levels.

Terpinen-4-ol is responsible for tea tree oil's broad-spectrum antimicrobial activity and makes it a well-researched option for acne.

Clinical studies support 5% tea tree oil as an effective topical treatment for mild to moderate acne. A study with 124 patients compared 5% tea tree oil gel to 5% benzoyl peroxide and both reduced acne (though tea tree oil worked more slowly).

Besides acne, it is also seen in anti-dandruff shampoos and scalp treatments for it's antimicrobial and anti-seborrheic properties.

Safety-wise, the allergic potential of low concentrations on healthy skin is considered low. However, oxidized (old or improperly stored) tea tree oil is a stronger sensitizer.

Irritation can also occur if using the undiluted oil on skin; it's best to use this ingredient as part of a carefully crafted cosmetic formula. This is because regulations require tea tree oil in cosmetics to be stabilized to prevent degradation.

This ingredient has been deemed safe up to 2% in shampoo, 1% in cleansers, and 0.1% in face cream by the EU's Scientific Committee on Consumer Safety (SCCS).

There is some lab evidence that tea tree oil is antifungal against Malassezia, but it is a supportive option at best and not a replacement for proven antifungal treatments.

For instance, Habanolide is a proprietary trade name for a specific aroma chemical. When used as a fragrance ingredient in cosmetics, most aroma chemicals fall under the broad labeling category of “FRAGRANCE” or “PARFUM” according to EU and US regulations.

The term 'parfum' or 'fragrance' is not regulated in many countries. In many cases, it is up to the brand to define this term.

For instance, many brands choose to label themselves as "fragrance-free" because they are not using synthetic fragrances. However, their products may still contain ingredients such as essential oils that are considered a fragrance by INCI standards.

One example is Calendula flower extract. Calendula is an essential oil that still imparts a scent or 'fragrance'.

Depending on the blend, the ingredients in the mixture can cause allergies and sensitivities on the skin. Some ingredients that are known EU allergens include linalool and citronellol.

Parfum can also be used to mask or cover an unpleasant scent.

The bottom line is: not all fragrances/parfum/ingredients are created equally. If you are worried about fragrances, we recommend taking a closer look at an ingredient. And of course, we always recommend speaking with a professional.

It works by disrupting microbial cell membranes and enzymes, and is a broad-spectrum protector that works exceptionally well against molds, yeasts, and gram-positive bacteria.

You'll likely see it paired with methylparaben to cover the full range (including gram-negative bacteria).

This ingredient is effective at low concentrations (~0.2-0.5%) and stable across a wide pH range (4.5-7.5 pH). It's effectiveness drops off above pH 8 and it can lose potency when combined with non-ionic surfactants like polysorbate 80 due to micellization.

The regulatory bodies have concluded this ingredient to be safe as used in cosmetics. The EU has capped it at 0.14% and combined parabens are not to exceed 0.8%.

While parabens do cross the stratum corneum, only about 1% remains for absorption into the body. This is because most of it is metabolized within living skin.

Using high concentrations of Potassium Hydroxide have shown to irritate the skin.

Dipropylene glycol is technically an alcohol, but it belongs to the glycol family (often considered part of the ‘good’ alcohols). This means it is hydrating and gentle on skin unlike drying solvent alcohols like denatured alcohol.

As a masking agent, Dipropylene Glycol can be used to cover the smell of other ingredients. However, it does not have a scent.

Studies show Dipropylene Glycol is considered safe to use in skincare.

Hexyl Cinnamal is not water soluble but is soluble in oils.

Limonene acts as an antioxidant, meaning it helps neutralize free radicals.

When exposed to air, oxidized limonene may sensitize the skin. Because of this, limonene is often avoided by people with sensitive skin.

The term 'fragrance' is not regulated in many countries. In many cases, it is up to the brand to define this term. For instance, many brands choose to label themselves as "fragrance-free" because they are not using synthetic fragrances. However, their products may still contain ingredients such as essential oils that are considered a fragrance.

Some people may experience allergies from this dye, especially asthmatics and those with an aspirin intolerance.