Rihanna Concert -- Herpe Days Are Here Again

A woman claims she got a souvenir at a Rihanna concert that will last her a lifetime ... herpes.

Starkeema Greenidge claims in a new lawsuit she was at a Rihanna concert at Barclays Center in Brooklyn when she was approached by a M.A.C. rep, who was hawking lipstick samples.

Greenidge claims the rep applied the RiRi Woo, red lipstick -- endorsed by Rihanna -- to her upper lip, told her to press her lips together and spread it around.

The suit claims the lipstick had been previously applied to the lips of others at the concert, and someone had the herp.

Greenidge told TMZ ... the day after the concert, "My whole lip was irritated and hugely swollen." Greenidge says she went to a doctor and he told her she had herpes.

The suit accuses M.A.C. of shoddy business practices -- applying lipstick directly from the tube instead of using either disposable samples or individual swabs.