What Is Ammonium Hydroxide?
Ammonium hydroxide is a clear water-based solution of ammonia gas that carries the chemical shorthand NH4OH. The ammonia itself can be sourced from natural fermentation processes or produced industrially through the Haber-Bosch method, which combines nitrogen from the air with hydrogen derived from natural gas. Once the gas is captured it is simply bubbled into purified water, creating the alkaline liquid used in cosmetics.
Historically, household cleaners were the first products to make use of ammonium hydroxide’s high pH. As cosmetic science advanced formulators noticed its ability to keep formulas stable, paving the way for its inclusion in skin and hair care starting in the mid-20th century. Today you will most often see it on the ingredient list of hair dyes, chemical peels, peel-off masks, liquid foundations, serums, lotions and some nail products where precise pH control is critical.
Ammonium Hydroxide’s Cosmetic Benefits/Uses
In beauty products ammonium hydroxide pulls its weight by serving two main technical roles:
- Buffering: It helps keep the product’s pH within a narrow, skin-friendly range. A stable pH guards against spoilage, preserves the activity of other ingredients and reduces the chance of irritation caused by unexpected shifts in acidity.
- Denaturant: When added to formulas that contain ethanol it renders the alcohol undrinkable. This discourages misuse and allows brands to use cosmetic-grade alcohol without paying beverage taxes which in turn keeps product costs lower.
Who Can Use Ammonium Hydroxide
Products that include ammonium hydroxide in low, regulated amounts are generally acceptable for normal, oily and combination skin because the ingredient itself does not linger on the skin after the formula is adjusted. People with sensitive, very dry or compromised skin conditions such as eczema should proceed with extra caution because high-pH ingredients can aggravate existing irritation.
Ammonium hydroxide is synthetically produced from mineral sources, not animals, so it is considered suitable for both vegetarians and vegans.
Current cosmetic safety assessments find no evidence that the small concentrations used in skincare or hair dye pose a unique risk to women who are pregnant or breastfeeding. Still, this is not medical advice and anyone who is pregnant or nursing should review any new product with a qualified healthcare provider.
The ingredient does not cause photosensitivity, so it will not make skin more prone to sunburn. It is also compatible with common actives like vitamin C, niacinamide and peptides once the finished product’s pH is set correctly.
Potential Side Effects/Adverse Reactions
Reactions to topical ammonium hydroxide vary from person to person. The points below outline potential side effects, but most people will not experience them when the ingredient is used at the low levels allowed in cosmetics.
- Skin stinging or burning
- Temporary redness or flushing
- Dryness or tightness
- Eye irritation if the product accidentally comes into contact with the eyes
- Worsening of pre-existing dermatitis or eczema
If any of these effects occur stop using the product immediately and seek advice from a medical professional.
Comedogenic Rating
Rating: 0/5 – Ammonium hydroxide is a water-based alkaline solution that leaves no oily or waxy residue on the skin, so it does not block pores or feed acne-causing bacteria. Because it is used only in tiny percentages to fine-tune pH and usually neutralizes during manufacturing, its likelihood of triggering breakouts is virtually nil. This makes it acceptable for people who are prone to acne or congestion. While not comedogenic, very high pH can temporarily dry skin which may prompt some individuals to produce more surface oil, so balanced formulations remain important.
Summary
Ammonium hydroxide acts mainly as a buffering agent and a denaturant. By nudging a formula toward the desired pH it keeps preservatives active, stabilizes sensitive actives and ensures the finished product feels comfortable on the skin. When paired with ethanol it denatures the alcohol, preventing misuse and reducing tax costs for manufacturers. You will not see it marketed with fanfare since it is a behind-the-scenes workhorse most common in hair dyes, certain peels and a handful of skincare products.
Regulatory reviews conclude that the low concentrations allowed in cosmetics are safe for general use, though people with very sensitive or compromised skin should still take care with high-pH formulations. As with any new product a quick patch test is a smart habit to confirm personal tolerance.