A rash guard shirt is a form-fitting athletic shirt made of spandex, nylon, or polyester. It is designed to protect the skin from chafing, sunburns, and board rash. Rash guards were originally developed for surfers who experienced irritation to the skin from sand and residue on their surfboards. They are now used by anyone spending time in or near water, including swimmers, kayakers, and stand-up paddleboarders. Rash guards are also used as sun protective clothing, as they offer some protection from the suns harmful UV rays.

Rash guards are not meant to keep the body warm, unlike wetsuits, as they are not as thick and do not trap body heat as well. They can actually have a cooling effect on the body because of their material and how tight they lay on the skin. Rash guard shirts are generally made of athletic fabrics like polyester, which are lightweight, quick-drying, flexible, durable, naturally antibacterial, and water-wicking. They are designed to fit snug and close to the body, allowing for free and easy movement in the water.

Some key features of rash guard shirts include:

• Rash Prevention: Rash guards protect the skin from rashes caused by abrasion or by sunburn from extended exposure to the sun. They are usually worn by themselves when surfing in weather too warm for a wetsuit to prevent chafing from sliding on and off of the waxed surface of the surfboard.

• Sun Safety: Rash guards are designed to add extra coverage to basic swimwear to prevent sunburns. Most rash guards are manufactured with Ultraviolet Protection Factors (UPF) to ensure efficient sun protection.

• Swim Shirts: Rash guards are sometimes referred to as swim shirts or surf shirts, which feature the same materials and technology as rash guards but with a more relaxed fit, designed to look and feel like a t-shirt.

In summary, a rash guard shirt is a type of athletic shirt made of spandex, nylon, or polyester that is designed to protect the skin from chafing, sunburns, and board rash while spending time in or near water.