Blood-filled pimples are most commonly caused by a condition called cystic acne. Cystic acne occurs when facial hair follicles become clogged and fill with blood and pus, says Proactiv. The hormone androgen, which increases during the teen years, contributes to the formation of cystic acne, explains WebMD.
Cystic acne happens when a bacterial infection occurs deep in the skin. The infection causes large, red, painful bumps or nodules to form deep under the surface of the skin. The outermost layer of the nodule is filled with blood, with a layer of pus underneath. Cystic acne is hereditary and is most common in young men, although women get it as well, notes WebMD.
Never attempt to pop blood-filled pimples caused by cystic acne, advises Proactiv. If the pimples are popped, the bacterial infection may spread to the rest of the face, causing further breakouts. Cystic acne is the most severe form of acne, and it requires immediate dermatological treatment, explains WebMD. If left untreated, cystic acne can cause deep scarring and disfigurement. The most commonly prescribed treatments for cystic acne include oral antibiotics, prescription-strength topical creams or gels, isotretinoin pills, and birth control pills, which regulate the hormones of women who suffer from cystic acne.