DIY Cosmetics — Risks, Safe Ingredients and What You Should Never Make Yourself

Avocado face masks, vitamin C serum mixed up in the kitchen, a coconut-oil cream “with no chemicals” — the internet is full of DIY cosmetic recipes. Some of them are safe and effective. Others can seriously harm your skin. So how do you tell them apart?

The main risks of DIY cosmetics

1. Microbial contamination

This is the biggest threat — and the one people most often downplay. Professional cosmetics contain preservative systems that protect the product from bacteria, fungi and mould. A homemade cream with no preservative is the perfect incubator for microorganisms.

• Bacteria can multiply within 24–48 hours in a water-based product.
• Mould isn't always visible to the naked eye — it can grow inside the product.
• Applying a contaminated cosmetic to your skin risks infections, pus-filled lesions and, in the worst case, sepsis.

Even if you add a preservative, you have no way to verify that it actually works. Professional labs run challenge tests — something that's impossible to do at home.

2. pH errors

The skin's pH is around 4.5–5.5. Products with too low a pH (strong acids) can cause chemical burns, while those with too high a pH (soap, baking soda) can destroy the hydrolipid barrier.

• Glycolic acid needs a pH of 3–4 to work, but below 3 it becomes dangerous.
• Vitamin C (ascorbic acid) needs a pH below 3.5 — too low and it will burn your skin.
• Baking soda has a pH of around 8.5 — far too high for facial skin.

Without a pH meter (litmus paper isn't enough — you need a digital pH meter), you simply can't control this parameter with sufficient accuracy.

3. Lack of formula stability

Professional cosmetics are precisely balanced formulas. Emulsifiers hold the water and oil phases together, stabilisers prevent separation, and antioxidants protect the active ingredients from degradation.

• Vitamin C oxidises on contact with air and light — a homemade serum loses its effectiveness within days.
• Retinol is exceptionally unstable — it requires special packaging and formulation.
• Homemade emulsions separate, which means the active ingredients are unevenly distributed.

What can you safely make at home?

Not all DIY cosmetics are dangerous. Here are the categories where the risk is minimal:

Single-use masks

• Honey + oatmeal — a soothing mask for irritated skin. Honey has antibacterial properties.
• Plain yoghurt — contains lactic acid and exfoliates gently (though the effect is minimal).
• Banana + honey — a hydrating mask. Don't store it — use it straight away.

The key rule: only make as much as you'll use immediately. Never store homemade masks.

Oil blends

• Jojoba oil + grapeseed oil — a light blend for facial massage.
• Argan oil on its own — as the final step of your evening routine.
• Rosehip oil — rich in vitamin A, good for dry skin.

Oils don't contain water, so the risk of bacterial contamination is low. Just be sure to check whether the oil is comedogenic — look it up in the PurScore ingredient database.

Simple mechanical scrubs

• Sugar + oil — for the body (NOT the face). Sugar is too harsh for the delicate skin of the face.
• Ground oats — a gentler alternative, suitable for facial skin.

What you should NEVER make yourself

Vitamin C serum

Although recipes circulate online, a homemade serum with L-ascorbic acid is problematic: it's unstable, hard to set to the correct pH, and oxidises quickly. Professional formulas contain stabilisers (ferulic acid, vitamin E) that extend shelf life and boost effectiveness.

Retinol creams

Retinol requires airtight packaging, protection from light and precise concentration. Too much = a burn. Too little = no effect. There's no way to control this under home conditions.

High-concentration chemical peels

Glycolic acid above 10%, salicylic acid above 2%, TCA (trichloroacetic acid) — these are in-clinic procedures. At home it's all too easy to cause a chemical burn, hyperpigmentation or scarring.

SPF creams

Sunscreens require precise dispersion and efficacy testing. A homemade “SPF cream” offers no protection — it gives a false sense of security, which is worse than having no sunscreen at all.

Products with preservatives

Adding a preservative is no guarantee of safety. Some preservatives only work within a specific pH range, while others require synergy with other ingredients. Without testing, there's no way to know whether the preservative system actually works.

How to assess a DIY recipe from the internet

1. Contains water and no preservative? → Dangerous.
2. Uses acids without stating the pH? → Risky.
3. Promises results like a professional cosmetic? → Unrealistic.
4. Recommends storing it for longer than 24 hours? → Potentially dangerous.
5. Contains essential oils in large amounts? → Risk of irritation (max. 1% in a product).

Before you buy an ingredient for a homemade cosmetic, check it in the PurScore search tool — you'll find out whether it's safe and at what concentration to use it.

Summary

DIY cosmetics can be a fun hobby, but they won't replace professional formulas. If you want to experiment, stick to the safe categories: single-use masks, oil blends and simple scrubs. Anything that requires precise pH, stabilisation or a preservative system — leave it to the professionals.

Be sure to read our guide to INCI ingredient lists too, so you can better understand what's in the cosmetics you buy — and why their complex formulas make sense.