Before modern hair treatments, frizzy hair could only be smoothed by pressing it with an iron or by running it through the fingers of a jazz pianist. Achieve a noteworthy 'do with today's Groupon: for $120, you get a keratin treatment at Trichology Salon (a $300 value).

Trichology Salon's stylists not only care for their clients' hair but strive to educate them on how to keep their tresses healthy and ravishing between visits. Global Keratin–certified owner Jennifer and her team of stylists slather locks with a GKhair keratin treatment, silkifying each strand and building up resistance to humidity. Appointments take about 90 minutes, depending on the thickness and length of each individual mane, and prove to be an abiding investment as head-fronds enjoy three–five months of glossy bliss. After the treatment, frizzy hair calms its harried nerves, tight curls stretch into flaxen waves, and locks straighten into strands sleek enough for weaving into designer wedding gowns.

Some hair-smoothing products include the carcinogen formaldehyde, which may cause nosebleeds, headaches, vomiting, and respiratory problems, among other side effects. Learn more about the health risks here.