Ingredient review

Ammonium Hydroxide

INCI: Ammonium Hydroxide

Ammonium hydroxide is a common pH adjuster that helps other ingredients work better, but it can be irritating at high concentrations.

beautyskincarepH adjuster

In plain English

Ammonium hydroxide is a form of ammonia dissolved in water. In skincare and hair products, it's used in tiny amounts to adjust the pH—that is, how acidic or alkaline a product is. Getting the pH right helps other ingredients, like preservatives or active ingredients, work properly. You'll often find it in hair dyes because it helps open the hair cuticle so color can penetrate. While it's generally safe at low levels, it can be irritating to sensitive skin or eyes, especially in higher concentrations.

Quick decision guide

Useful, but context matters

Ammonium Hydroxide can be useful, but watch for some irritation potential.

Plain-English read

Treat this as a practical screening step before you compare products that contain this ingredient.

  1. Step 1Start with the score, then check the irritation and clogging risk before judging Ammonium Hydroxide.
  2. Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
  3. Step 3If a product stings, breaks you out, or worsens irritation, judge the finished formula and stop using it even if the ingredient scores well.

Score terms in plain English

Irritation risk

moderate

Can bother some users, especially with frequent use, damaged skin, or strong companion ingredients.

Clogging risk

low

Less likely to feel heavy or contribute to clogged pores for most skin types.

Evidence level

moderate

There is useful support, but formula details and claim strength still matter.

What it is

Ammonium hydroxide is a solution of ammonia gas in water. It's a weak base, meaning it raises the pH of a formula. In cosmetics, it's used as a pH adjuster and buffering agent to keep the product's acidity or alkalinity stable.

How it works

When added to a formula, ammonium hydroxide releases small amounts of ammonia gas, which raises the pH. This helps other ingredients function correctly—for example, it helps hair dye molecules penetrate the hair shaft. It also helps preserve the product by creating an environment where microbes are less likely to grow.

Pros

Effective pH adjuster

Ammonium hydroxide efficiently raises pH to the optimal range for hair dye penetration and product stability, ensuring consistent performance.

Volatile and evaporates

Unlike some other alkalis, ammonium hydroxide can evaporate from the hair after dyeing, reducing the risk of long-term residue buildup.

Cons and cautions

Potential irritant

At higher concentrations, ammonium hydroxide can cause skin redness, stinging, or eye irritation, especially in leave-on products.

Strong odor

The characteristic ammonia smell can be off-putting and may linger during application, though it usually dissipates quickly.

Best for

  • People using permanent hair dyes that require alkaline pH for color deposit
  • Anyone using well-formulated products where ammonium hydroxide is used at safe, low levels

Use caution if

  • Individuals with very sensitive skin, eczema, or broken skin, as it may cause stinging or irritation

Usage tips

Always use products containing ammonium hydroxide in a well-ventilated area to minimize inhalation of fumes.
If you have sensitive skin, do a patch test before using a product with ammonium hydroxide, especially hair dyes.

Safety summary

Ammonium hydroxide is considered safe in cosmetics when used at low concentrations (typically under 1% in leave-on products). Higher concentrations can cause irritation, so it is most common in rinse-off products like hair dyes. Regulatory bodies worldwide set limits to protect consumers.

Research notes

Studies show that ammonium hydroxide is an effective pH adjuster with low systemic toxicity at cosmetic-use levels. Skin irritation is dose-dependent, and most adverse reactions are mild and reversible. The Cosmetic Ingredient Review (CIR) panel has deemed it safe as used in cosmetics.

Common label clues

Typical concentration
Typically less than 1% in leave-on products; higher in rinse-off products like hair dyes
Regulatory status
Approved for use in cosmetics by the U.S. FDA and the European Commission, with concentration limits to ensure safety. In the EU, it is listed in Annex III of the Cosmetics Regulation with specific restrictions.
Common uses
Hair dyes, Hair relaxers, Skin cleansers, Moisturizers
Environmental note
Ammonium hydroxide is biodegradable and does not persist in the environment, but its production involves ammonia synthesis, which has an energy and carbon footprint.

Good to know

  • Ammonium hydroxide is not the same as household ammonia cleaner—cosmetic-grade is much more dilute and formulated for skin contact.
  • In hair dyes, ammonium hydroxide is often used alongside other pH adjusters to fine-tune the formula.

Common questions

What is Ammonium Hydroxide in beauty products?

Ammonium hydroxide is a form of ammonia dissolved in water. In skincare and hair products, it's used in tiny amounts to adjust the pH—that is, how acidic or alkaline a product is. Getting the pH right helps other ingredients, like preservatives or active ingredients, work properly. You'll often find it in hair dyes because it helps open the hair cuticle so color can penetrate. While it's generally safe at low levels, it can be irritating to sensitive skin or eyes, especially in higher concentrations.

What does Ammonium Hydroxide do in a beauty product?

When added to a formula, ammonium hydroxide releases small amounts of ammonia gas, which raises the pH. This helps other ingredients function correctly—for example, it helps hair dye molecules penetrate the hair shaft. It also helps preserve the product by creating an environment where microbes are less likely to grow.

Is Ammonium Hydroxide safe for most people?

Ammonium hydroxide is considered safe in cosmetics when used at low concentrations (typically under 1% in leave-on products). Higher concentrations can cause irritation, so it is most common in rinse-off products like hair dyes. Regulatory bodies worldwide set limits to protect consumers.

Who should be careful with Ammonium Hydroxide?

Individuals with very sensitive skin, eczema, or broken skin, as it may cause stinging or irritation

Research sources

Cosmetic Ingredient Review (CIR) - Ammonium Hydroxide Safety AssessmentOpenEuropean Commission CosIng Database - Ammonium HydroxideOpenU.S. FDA - Cosmetics IngredientsOpen

Ingredient reviews are educational and are not medical advice. Patch test new products and ask a licensed clinician about persistent irritation, allergies, pregnancy-specific questions, or diagnosed skin conditions.