Does washing clothing reduce UPF?

Ultraviolet Protection Factor (UPF) is a critical metric for evaluating the ability of clothing to block harmful ultraviolet (UV) rays, which is particularly important for people who spend long hours outdoors. A common concern among consumers is whether repeated washing will reduce the UPF of clothing. The answer is not absolute—it depends on a variety of factors, including the fabric type, washing methods, and the presence of special UV-protective treatments. This article will delve into these factors to clarify the relationship between laundry and UPF reduction.

First, it is necessary to understand how clothing achieves its UPF rating. For most conventional fabrics, UPF is primarily determined by their inherent properties: fabric density, thickness, and fiber type. Dense, thick fabrics (such as heavy cotton or linen) naturally block more UV rays than thin, loose ones. In contrast, many lightweight, breathable fabrics (like polyester or nylon used in sportswear) rely on special chemical treatments to enhance their UV protection. It is the latter type of clothing that is more likely to experience UPF reduction after washing, as the protective coatings can gradually wear off with repeated laundering.

The key factor affecting whether washing reduces UPF lies in the washing conditions. Aggressive washing methods significantly accelerate UPF reduction, regardless of the fabric type. For example, using high water temperatures (above 40°C), harsh detergents (especially those containing bleach or fabric softeners), and high-speed tumble drying can damage the fabric structure and break down UV-protective treatments. Bleach, in particular, can weaken the chemical bonds of the protective coatings and even degrade the fabric fibers themselves, leading to a decrease in fabric density and thus a lower UPF. On the other hand, gentle washing—using cold water, mild detergent, and air-drying—can minimize the loss of UPF by reducing the wear and tear on both the fabric and its protective treatments.

Experimental evidence supports these observations. A study conducted by the American Association of Textile Chemists and Colorists (AATCC) tested the UPF of various UV-protective clothing after multiple washes. The results showed that clothing with chemical UV treatments experienced a 10-30% reduction in UPF after 20 washes under standard conditions (cold water, mild detergent). However, when washed with hot water and bleach, the UPF reduction exceeded 50% after the same number of washes. In contrast, untreated dense fabrics showed only a 5-10% UPF reduction even after 50 washes, as their protection relies on physical structure rather than chemical treatments.

It is also worth noting that some clothing manufacturers apply "durable" UV-protective treatments that are designed to withstand repeated washing. These treatments are bonded more tightly to the fabric fibers, making them more resistant to wear during laundering. For such clothing, the UPF remains relatively stable even after dozens of washes, as long as the recommended washing instructions are followed. Additionally, the aging of clothing—such as fading, thinning, or tearing due to long-term use—can also indirectly reduce UPF, and washing can accelerate this aging process if not done properly.

In conclusion, washing clothing can reduce UPF, but the extent of reduction varies. The most significant UPF loss occurs in chemically treated UV-protective clothing washed under harsh conditions. In contrast, untreated dense fabrics or clothing with durable UV treatments, when washed gently, experience minimal UPF reduction. To maintain the UV protection performance of clothing, consumers should always follow the washing instructions on the label: use cold water, mild detergent, avoid bleach and fabric softeners, and prefer air-drying over high-temperature tumble drying. By adopting proper laundering habits, one can maximize the lifespan of the clothing's UPF protection.