Salicylic Acid (C₇H₆O₃) is a well-known organic compound characterized by its phenolic structure and anti-inflammatory as well as keratolytic (exfoliating) properties. It belongs to the beta hydroxy acid (BHA) family and occurs naturally in the bark of willow trees (Salix). Salicylic acid plays a crucial role in the treatment of numerous skin disorders and is one of the most effective ingredients used in anti-acne and exfoliating skincare products.

Chemical Structure

Molecular Formula: C₇H₆O₃
Chemical Name: 2-Hydroxybenzoic Acid
Structure: A benzene ring with two functional groups — a hydroxyl group (OH) at position 2 and a carboxylic acid group (COOH) at position 1.

This dual functionality gives salicylic acid both phenolic and carboxylic acid characteristics, contributing to its antibacterial activity and ability to penetrate skin pores effectively.

Physical and Chemical Properties

Property	Value / Description
Physical State	White crystalline powder
Melting Point	Approximately 158–161 °C
Solubility	Soluble in alcohol and ether; slightly soluble in water
pH (1% aqueous solution)	Acidic — around 2.4
Odor	Mild, phenolic
Stability	Relatively stable in acidic media; unstable in alkaline conditions

Applications of Salicylic Acid

In Skincare Products

Anti-acne treatment
Chemical exfoliant
Cleansing and unclogging pores
Sebum (oil) regulation

In Scalp and Hair Treatments

Dandruff control
Treatment of psoriasis and seborrheic dermatitis

In Pharmaceuticals

Mild anti-inflammatory agent
Active ingredient in topical ointments and creams

In Cosmetic Formulations

Used in toners, serums, masks, cleansers, and day/night creams
Often combined with niacinamide or retinol for enhanced results

Advantages of Salicylic Acid

Deep pore penetration: Unlike AHAs, BHAs are oil-soluble, allowing deeper absorption into the skin.
Exfoliating and anti-inflammatory properties: Effective against acne, blackheads, and whiteheads.
Sebum control: Helps regulate skin oil production.
Mild antibacterial and antifungal effects.
Enhances absorption of other active ingredients in formulations.

Disadvantages and Limitations

Possible irritation for sensitive skin: may cause redness, dryness, or flaking.
Use with caution during pregnancy and breastfeeding.
High concentrations may lead to burning or inflammation.
Incompatible with certain ingredients such as strong acids, pure Vitamin C, or retinol (when used simultaneously).