Salicylic acid (SA) is a phenolic phytohormone and is found in plants. It supports photosynthesis, transpiration, ion uptake and transport. SA also induces specific changes in leaf anatomy and chloroplast structure.
Salicylic acid is known for its ability to ease aches and pains and reduce fevers. These medicinal properties, particularly fever relief, have been known since ancient times, and it is used as an anti-inflammatory drug. It can also help with treating scalp itching, flaking, irritation, redness, and scaling due to psoriasis, dandruff, or seborrhea.
In modern medicine, salicylic acid and its derivatives are used as for example, methyl salicylate is used to soothe joint and muscle pain, and choline salicylate is used topically to relieve the pain of mouth ulcers.
Although toxic in large quantities, salicylic acid is used as a food preservative, a bactericidal, and an antiseptic agent.
Salicylic acid gel is a topical salicylate. It works by causing the skin to swell, soften, and then slough or peel in areas where it is applied.