The short answer: Pretty important if you don’t like itchy, scaly, red rashes. Due to varying laws from country to country on the allowable levels of chemicals in fabric, your clothing could be hopping around the globe carrying various substances that might irritate your skin, reports the Wall Street Journal.
According to Donald Belsito, a professor of dermatology at Columbia University Medical Center in New York with a specialty in contact dermatitis, sometimes you might even want to wash new clothing more than once before wearing it.
Many synthetic textiles get their hues from azo-aniline dyes, which can cause a severe skin reaction if you’re allergic to it and a less intense, yet still irritating reaction of itchy, dry patches of skin where it touches your skin.
It might take more than one washing to rinse out the dye, so you could get itchy red spots “especially near the areas where there is friction or sweating, like the waist, neck and thighs and around the armpits,” Dr. Belsito told the WSJ.
If you’re actually allergic to those dyes, he says you might need to avoid them altogether as it could be stubborn about leaving even after multiple washings.
Another irritant could be formaldehyde resins used to keep blends from wrinkling and cut down on mildew. These resins can cause two forms of eczema — allergic contact dermatitis and irritant contact dermatitis — both which have symptoms like flaky skin and rashes.
You also don’t know who’s been touching your clothing or trying it on in the store before it comes home with you, making it possible that germs and other critters could be hiding out in the fabric.
“I have seen cases of lice that were possibly transmitted from trying on in the store, and there are certain infectious diseases that can be passed on through clothing,” Dr. Belsito says, noting that scabies can also infest clothing.
Dr. Belsito’s advice is to wash all new clothing at least once with a double rinse before wearing, no matter what the fabric.
“In terms of hygiene, it’s a very good thing to do,” he says. “Being a dermatologist, I’ve seen examples of some strange stuff, so I don’t take any chances.”
Do You Need to Wash New Clothes Before Wearing Them? [Wall Street Journal]