What applies to returning underwear
Short answer: In many shops underwear can only be returned in unopened packaging. If you open the pack, the right of return lapses for hygiene reasons.
Why the rule exists
Underwear and swimwear lie directly against the skin. An item that has been out of its packaging cannot be sold again. The rule is permitted in the EU for exactly that reason and is stated in the shop's terms.
What you can do instead
Measure a pair you already own and compare with the table before ordering. That is the only way to get it right without opening the pack. See bamboo underwear for men.
When it is a fault
If the item is defective or wrongly delivered, your rights apply regardless of the packaging. See bamboo underwear for women and bamboo briefs for women.
Frequently asked questions
Does it apply to socks as well
Often not. Socks can usually be returned if they are unworn.
What if the packaging is a bag with tape
If you open the tape, the packaging is broken. Read the terms first.
Can you try underwear on without opening it
No. That is why the measurements matter more here than anywhere else.