Cotton is more breathable than polyester, but each fabric has its own benefits depending on what it is being used for. Cotton is a popular material for sheets because it is breathable, soft and durable, but it is considered a poor choice for athletic clothing.
Cotton is a good choice of fabric for people with sensitive skin because it is less irritating, although clothing made of cotton tends to absorb sweat, which leads to chafing. This is because the fabric can absorb approximately 24 to 27 times its weight in water. Polyester is a petroleum-based synthetic fabric that wicks away moisture to ensure that skin stays dry. Polyester is less absorbent than cotton, allowing the material to dry much faster.