Not according to this guide from the Office of Fair Trading:
http://www.oft.gov.uk/shared_oft/business_leaflets/general/oft698.pdf
Paragraph 3.42 says: "We are conscious of concerns about reselling items which may raise concerns about hygiene. However, the DSRs do not link cancellation rights with a supplier’s ability to resell items as new."
In other words, no hygience exceptions (and no mention of makeup or pierced earrings as an exception, although there is a specific exemption for CD ROMs).
Of course, it has to be borne in mind that the distance selling regulations are separate from the normal returns policy (as pointed out by John Bennett via Graham on the Gems TV thread). If Mayday decides to purchase the earrings and then decides that she wants to return them, she should send an e-mail to TJC within 7 days stating that she is cancelling her contract with them under the distance selling regulations, and is returning the earrings to them for a refund. If she follows this procedure, they are obliged to refund her original postage charge as well as the price of the earrings.
John Bennett also pointed out that, under the DSR you have to cancel the whole order and not just return part of it, so Mayday should avoid ordering any other items in the same order as the earrings, since if she sent them back she would have to send back the other items also.
I'm not a lawyer (although I've been accused of thinking like one) but of course John Bennett is, so I'm sure he knows what he's talking about on this.
Meanwhile, I wish TJC would come to their senses over their ridiculous return policy on earrings, and treat customers fairly as all the other channels do. To be honest, even the little plastic bags the other channels use are un-necessary; the earring posts can simply be wiped with an alchol wipe to sterilise them. (In the USA - surely a more litigious society than here - I have actually been allowed to try on pierced earrings in shops.) And what about QVC? - the last time I purchased earrings from them (which granted was several years ago), they arrived unsealed and there was no problem about returning them. It is hard to escape the conclusion that TJC are just using this as an excuse to get out of giving refunds.