Standard period underwear is not recommended for use in a pool or any body of water because its fundamental design is compromised upon full immersion. While highly effective for managing menstrual flow on land, the absorbent core is not engineered to handle the massive, continuous volume of external water. When submerged, the underwear immediately absorbs the surrounding water, which uses up its capacity and renders it ineffective for its intended purpose. This saturation causes failures in function and comfort, making them unsuitable for swimming.
How Standard Period Underwear Functions
Standard period underwear relies on a specialized, multi-layered construction to manage and contain menstrual fluid. The innermost layer, which rests against the skin, is moisture-wicking, quickly pulling fluid away from the body to maintain a dry feeling. Beneath this layer is the absorbent core, made of highly absorbent fibers that trap and lock in menstrual fluid. This core can hold the equivalent of several tampons or pads, depending on the design. The entire system is backed by a leak-proof barrier, often made of polyurethane laminate (PUL), which prevents the absorbed fluid from passing through to clothing.
Why Water Immersion Compromises Absorption
The core reason standard period underwear fails in water is due to capillary action. The highly porous absorbent core, designed to quickly draw in menstrual fluid, cannot distinguish between blood and pool water. When submerged, the massive volume of surrounding water is rapidly pulled into the core, acting like a sponge.
This immediate saturation has multiple negative consequences. First, the core’s capacity to absorb menstrual flow is instantly used up by the external water, leaving no room for the blood it is meant to manage. Second, the garment becomes significantly heavier and bulkier as the absorbent material swells with the retained water, leading to discomfort and a noticeable “wet diaper” feeling. The integrity of the leak-proof barrier can also be compromised, as the volume of absorbed water can lead to dilution of the menstrual fluid within the core. Furthermore, the garment retains external water, which raises hygiene concerns since pool water may contain chemicals or natural water can harbor bacteria.
Options for Managing Periods While Swimming
Several effective alternatives exist for swimming while menstruating that do not rely on the external absorption mechanism of standard period underwear. The most reliable options involve internal collection methods that prevent menstrual fluid from ever reaching the water.
Menstrual cups and discs are highly recommended for swimming. They are inserted into the vaginal canal to collect the flow, creating a secure, leak-proof seal. This seal prevents menstrual fluid from escaping and stops external water from entering the cup, allowing for worry-free swimming.
Tampons are another viable option, as they absorb the flow internally before it exits the body. Since tampons can absorb some surrounding water, it is advised to insert a fresh one immediately before swimming and change it again immediately after getting out of the water.
A newer, specialized product is period swimwear, which differs structurally from standard period underwear. This swimwear is engineered with a hydrophobic, water-repelling outer shell and a thinner absorbent core. The design focuses on a leak-proof barrier and compression to contain light to moderate flow while repelling external water, making it suitable for water activities.