Antiperspirant vs Deodorant — What's the Difference and What's Really in the Ingredients?

Antiperspirant and deodorant — most people use the two terms interchangeably, but from a cosmetic-chemistry standpoint they are two completely different product categories. An antiperspirant is classed as a cosmetic product with a quasi-medical action, because it interferes with the physiological process of sweating. A deodorant only neutralises odour. That distinction has real consequences for your skin and your health.

How does an antiperspirant work? The mechanism of aluminium salts

The key active ingredient in every antiperspirant is an aluminium salt — most often Aluminum Chlorohydrate (ACH), and less frequently Aluminum Zirconium Tetrachlorohydrex Gly (more effective and popular in the US). The mechanism of action is purely physical:

1. Aluminium salts dissolve in sweat and form a gel-like structure.
2. This gel plugs the openings of the sweat ducts, reducing the amount of sweat released by 20–50%.
3. The effect lasts 24–48 hours but disappears after a few washes — the gel plug is removed mechanically.

It's worth knowing that antiperspirants don't block sweating entirely. The body has 2–4 million sweat glands, and an antiperspirant is applied to only a small area of the underarms. The body's thermoregulation is not put at risk.

The safety of aluminium — what does the science say in 2020?

The debate over the safety of aluminium salts in antiperspirants has been running since the 1990s. Here is the current state of knowledge:

The 2020 SCCS (Scientific Committee on Consumer Safety) opinion

In 2020 the European Commission's Scientific Committee on Consumer Safety issued an opinion stating that aluminium salts at concentrations of up to 6.25% (expressed as aluminium) are safe in antiperspirants, even with daily use. This concentration covers the vast majority of products on the market.

The SCCS did, however, point out that earlier limits (up to 10.6% aluminium) may be too high, and proposed lowering the safety threshold as a precaution. The opinion took into account data on aluminium penetration through the skin — both healthy skin and skin after shaving.

Aluminium and breast cancer — myth or risk?

The hypothesis linking aluminium in antiperspirants to breast cancer, popularised in 2003 by the McGrath study, has not been confirmed in any large epidemiological study. A meta-analysis in Critical Reviews in Toxicology (2014) found no statistically significant association. The American Cancer Society, the WHO and the SCCS all agree that there is insufficient evidence for such a risk.

How does a deodorant work?

A deodorant doesn't block sweating — instead, it neutralises the smell of sweat. Sweat itself is odourless; the characteristic smell arises when bacteria (mainly Staphylococcus hominis and Corynebacterium) break down the fatty acids in apocrine sweat. Deodorants work in three ways:

• Antibacterially — they reduce the population of odour-causing bacteria (e.g. Triclosan, Farnesol, essential oils).
• By absorption — they soak up moisture and odour (Talc, corn starch, diatomaceous earth).
• By fragrance — they mask the smell with perfume compositions.

Natural alternatives — what does the research say?

The growing popularity of "clean beauty" is driving demand for aluminium-free deodorants. But do natural ingredients really work?

Zinc Ricinoleate (zinc ricinoleate)

The zinc salt of ricinoleic acid, derived from castor oil. It works by absorbing odour molecules — binding volatile fatty acids and sulphides before they reach the olfactory receptors. In vitro studies show a 70–85% reduction in odour intensity. It doesn't block sweating and has no antibacterial action — it works purely on "odour".

Saccharomyces Ferment Filtrate (yeast ferment)

A fermentation product of Saccharomyces cerevisiae yeast, containing proteolytic enzymes. It breaks down sweat proteins before bacteria can metabolise them into foul-smelling compounds. A relatively new ingredient in natural deodorants, with a limited but promising evidence base.

Baking soda (Sodium Bicarbonate)

A popular ingredient in DIY and "natural" deodorants. It effectively neutralises the acidic breakdown products of sweat, but it has a pH of 8.3, which disrupts the acidic pH of underarm skin (4.0–5.5). In many people it causes irritation, redness and stinging. Dermatologically, it's a controversial ingredient.

Alum stone (Potassium Alum)

Contrary to marketing claims, alum stone contains aluminium — it is potassium aluminium sulphate. Its particles are larger than those in ACH, so penetration through the skin is lower, but this is not an "aluminium-free" product.

Irritation after shaving — when an antiperspirant does harm

Shaving removes the stratum corneum and creates micro-injuries through which aluminium salts can penetrate more deeply. A study in the Journal of Applied Toxicology (2019) found that aluminium penetration through shaved skin is six times higher than through intact skin. Dermatologists' recommendation: apply antiperspirant in the evening, to dry skin, at least 6–8 hours after shaving.

Ingredient comparison — table

• Typical antiperspirant: Aluminum Chlorohydrate, Cyclopentasiloxane, Steareth-2, PPG-14 Butyl Ether, Parfum, BHT.
• Typical deodorant: Alcohol Denat., Aqua, Parfum, Triethyl Citrate, Zinc Ricinoleate, Cocamidopropyl Betaine.
• Natural deodorant: Caprylic/Capric Triglyceride, Sodium Bicarbonate, Zinc Ricinoleate, Tocopherol, Citrus Aurantium Dulcis Peel Oil.

Want to know what's hiding in your antiperspirant? Scan it in the PurScore search engine.

Which one should you choose? Practical tips

• Heavy sweating (hyperhidrosis)? An ACH antiperspirant is the medical standard — a natural deodorant won't help.
• Sensitive skin after shaving? A deodorant without aluminium or alcohol, containing zinc ricinoleate.
• Everyday comfort without excessive sweating? An antiperspirant with an aluminium concentration of up to 6.25% (safe per SCCS 2020).
• "Clean beauty" preferences? A deodorant with Zinc Ricinoleate or yeast ferment — effective against odour, but not against the amount of sweat.

Analyse the ingredients of your deodorant in the PurScore ingredient database so you can make an informed choice between sweat control and a natural approach.