What is Period Underwear?
Last updated 2026-05-24
Period underwear is absorbent underwear designed to be worn during menstruation in place of (or alongside) tampons, pads, and cups. The garments contain built-in moisture-wicking and absorbent layers that hold menstrual flow without leaks, then are washed and reused. The category was pioneered by Thinx in 2014 and has expanded significantly. Leading brands now include Thinx, Knix, Saalt, Modibodi, Aisle, and Period Company. Different absorbencies — light, moderate, heavy, super — let users match the garment to their flow stage. Most pairs hold 4 to 6 tampons' worth of liquid; heavy versions hold up to 10 tampons' worth. The environmental case is significant. The average menstruator uses 5,000+ disposable period products in a lifetime, generating substantial landfill waste. A period underwear rotation (typically 5 to 10 pairs) replaces this with washable, reusable garments. The financial math also favors period underwear over time — initial $20 to $40 per pair offset by years of reduced disposable purchases. The category has faced some safety concerns around PFAS (forever chemicals) in some early products; reputable current brands now PFAS-free.
Sara built a 7-pair Knix rotation to cover a typical 5-day period with a few backup pairs. Two years in, she'd eliminated tampons and pads entirely for her flow, saved an estimated $300, and generated almost no period-related waste.
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Questions, answered.
Does period underwear really not leak?
Quality period underwear from established brands holds reliably when matched to flow level. Leaks are usually from undersized capacity (wearing light pairs on heavy days) or going too long between changes. Match the absorbency level to your actual flow stage.
How do you clean period underwear?
Rinse with cold water until water runs clear, then machine-wash with cold water and mild detergent. Air dry — high heat damages the absorbent layers. Most period underwear lasts 2 to 5 years with proper care, depending on usage frequency.
Is period underwear safe? I heard about PFAS concerns.
Early period underwear (including some Thinx products) was tested with PFAS contamination, leading to lawsuits and reformulations. Current products from reputable brands are PFAS-free and certified. Check brand certifications and recent independent testing if PFAS is a concern.