Boil vs. cyst vs. carbuncles

It can be easy to confuse boils with carbuncles or cysts, but there are differences.

Identifying boils: Differences from cysts and carbuncles

A carbuncle is simply a few boils grouped together. A cyst, on the other hand, is a smooth, round, closed sac under your skin filled with fluid or semisolid material.

Boils and cysts can both look like bumps on your skin. The main difference between a cyst and a boil is that a boil is a bacterial or fungal infection.

Most cysts are slow-growing and benign (noncancerous), and they aren’t contagious. Boils, on the other hand, can spread bacteria or fungi on contact.

The following table gives an overview of the differences between a boil, a cyst, and a carbuncle:

TypeSymptomsCausesRisk factorsTreatment
Boilpresents as a red pimple that may swell and ooze; grows rapidly and is usually painfulresults from a bacterial or fungal infectionrisk factors include skin conditions like acne, psoriasis, or eczema; close contact with someone who has a boil; compromised immune system; diabetes; obesityapplying a warm, moist compress; keeping a clean bandage over the boil; avoidingpicking; if symptoms don’t improve, draining the puss, cleansing the area, and treating with antibiotics may be necessary
Carbunclesimilar to single boils but may be accompanied by fever; often occurs at the back of the neck and extends deeper into the tissue than boilssimilar to boils, caused by an infection, most commonly from staph bacteriasimilar risk factors to boilssimilar to boils, but even more important to release the puss either with a drawing salve ointment or surgical draining followed by cleansing the wound; antibiotics may be necessary and may be administered intravenously
Cystpresents as a smooth nodule under the skin that’s movable, grows slowly, and usually isn’t painful unless inflamedthe cause of many cysts is unknown but may include an injury, swollen hair follicle, the human papillomavirus (HPV), or chronic ultraviolet light; some types of cysts may be hereditary, and some are associated with disorders like Gardner’s syndromepeople assigned male at birth may be more at risk since most types of cysts are more common in them than in people assigned female at birthmost cysts need no treatment, and they may disappear on their own, but they may recur; treatment can involve antibiotics or surgery to drain the cyst (usually if the cyst can move under the skin)