The severity of the event can be lessened with Cephalaxin and/or a lactation massager (specialized waterproof vibrator).
See also WebMD.com's article about Mastitis.
Frequently Asked Questions
About Inducing Lactation
Are there health concerns from breastfeeding or letting someone drink my milk?
It's perfectly fine to try another person's breast milk if you know their health history. Breast milk is a body fluid and therefore it's possible to transmit pathogens. The next biggest concern is Mastitis (warning:NSFW) which can be lessened with Lecithin and a proper latch technique. The Piercings and Lactation page (warning:NSFW) addresses this concern as well.