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What Is a Draining Sinus?

A Draining Sinus Is a Large, Red, Painful Lesion That Develops from the Merging of Multiple Acne Cysts

By: Dan Kern, Acne.org Founder & CSO
Last updated: February 07, 2020

The Essential Information

Draining sinuses are huge, tender, bumps that form when multiple cysts combine under the skin. They are the largest type of a lesion found in "nodulocystic" acne, often referred to simply as "cystic acne," and are very likely to leave behind scars.

Draining sinuses get the name "draining" because they contain pus that can spontaneously leak onto the skin. However, they should never be popped.

Treatment of an existing draining sinus: cortisone shots, incision and drainage, aspiration, surgical removal, cryotherapy

Preventing a draining sinus by treating cysts before they merge: benzoyl peroxide, isotretinoin (Accutane®), oral antibiotics, cortisone shots, cryotherapy, and/or hormonal treatment (females only). Photodynamic therapy is a new treatment that also shows promise.

The Science

Draining sinuses are extra-large acne lesions that develop when multiple acne cysts merge to form one huge, inflammatory lesion. They appear as raised, red, soft bumps around 2-5 centimeters long that occasionally leak pus. They tend to be elongated in shape, whereas single acne cysts are usually are more circular. Draining sinuses most commonly arise on the face, near the nasolabial fold (the area running from the sides of the nose down to the sides of the mouth - often called "smile lines" or "laugh lines"). Once a draining sinus develops, it often persists on the skin for months or even years, leaves large scars, and will not resolve without treatment. Most often, draining sinuses occur only with especially severe forms of acne, including acne conglobata, acne fulminans, pyoderma faciale, and acne inversa.1,2

Inside of a draining sinus lies pus, acne bacteria, inflammatory cells, skin cells, hair remnants, and skin oil. Occasionally, a draining sinus will contain disease-causing bacteria in addition to the normal bacteria found in the skin (P. acnes).

Formation of a Draining Sinus

A draining sinus forms from the merging of multiple acne cysts.

Formation of an acne cyst

Acne develops when a hair follicle (pore) becomes clogged with skin cells skin oil. A clogged pore is the ideal environment for acne bacteria, which begins to divide rapidly inside the pore. In response to this, the body produces inflammation that damages the pore and causes it to rupture. If a small portion of the pore wall ruptures, then a run-of-the-mill pimple forms within the upper layers of the skin. However, if the entire pore explodes, a cyst can result.

Formation of a draining sinus

Draining sinuses form when multiple acne cysts combine to form one large, interconnected lesion. During this merging, a series of interconnected tunnels forms, which connects the multiple cysts in the deep layers of the skin. These tunnels consist of multiple openings that lead to the surface of the skin. Inside the cysts and tunnels there is a mix of pus, bacteria, inflammatory cells, skin cells, hair remnants, and skin oil. These contents can spontaneously leak onto the surface of the skin.1,2

Draining Sinus

What Causes Draining Sinuses?

Scientists do not fully understand what causes the formation of a draining sinus in individuals with acne cysts. Researchers have found that people with diseases of the sinus tract or who have family members with a sinus tract disease tend to be more likely to develop draining sinuses. However, the reason behind this connection is unknown.

Treatment Options for Draining Sinuses

Once a draining sinuses is formed, a dermatologist can still treat it with a variety of treatments. Like acne cysts, draining sinuses should never be attempted to be popped, as this will only cause the contents to be expelled deeper into the skin, worsening the lesion, permanently damaging the skin, and leaving behind severe scarring.

Draining Sinus Treatments

Draining sinus treatments

Draining sinuses are difficult to treat, and dermatologists are not yet sure of the best method to treat them. However, there are several options to clear draining sinuses once they form in the skin. Caution: Never try any of these at home. It will result in a more severe lesion, potential infection, and potentially massive scarring.

  1. Intralesional shots (cortisone shots): Intralesional shots, often called cortisone shots, involve injecting an anti-inflammatory medication called a corticosteroid directly into the draining sinus. Corticosteroids are different from steroids taken by bodybuilders, as corticosteroids work to decrease swelling, while other steroids work to increase muscle. The introduction of steroids into the draining sinus decreases the swelling and size of it, without increasing the risk of scarring.
  2. Incision and drainage: Due to the severity of a draining sinus, surgical intervention that cuts and drains the lesion is often required. This procedure involves cutting open the draining sinus with a needle or blade in sterile conditions and draining its contents. However, this treatment option is only moderately effective, as draining sinuses will likely refill. Further, this procedure also increases the risk of scarring.
  3. Aspiration: The term aspiration refers to inserting a thick needle into the lesion and removing the contents. This treatment is likely only temporary because the draining sinus will probably refill. However, aspiration is less likely to cause scarring.
  4. Surgical removal: In especially stubborn draining sinuses, when other treatment options do not work, the draining sinus will have to be removed surgically from the skin. Although this option is most likely to cure the draining sinus, it will leave large scars.
  5. Cryotherapy: Cryotherapy is a procedure performed by freezing an acne lesion to hasten its healing. Cryotherapy for a draining sinus is performed by applying a liquid nitrogen spray to the lesion for about 15 seconds, which quickly freezes it. Freezing of the draining sinus prevents its growth and supports its healing. However, cryotherapy is not the preferred treatment option for draining sinuses, as it does not work well on every skin type, and it can leave severe scars if performed improperly.3

Acne Cyst Treatments

Draining sinus prevention: acne cyst treatments

By treating acne cysts before they can develop into draining sinuses, the formation of a draining sinus can be prevented. There are several treatment options for acne cysts.

  1. A properly applied benzoyl peroxide regimen: To prevent future nodules, treating the skin gently and applying benzoyl peroxide in the right manner can stop the development of any type of acne lesion, including cysts.
  2. Isotretinoin + steroids: Isotretinoin (Accutane) is an oral medication that permanently and irreversibly changes the skin and body, and therefore it is a treatment of last resort, only being approved for severe, widespread cystic acne. However, in the case of severe acne that comes with draining sinuses doctors sometimes advise its use, often in combination with oral corticosteroids, which help quickly reduce inflammation. Patients will often take corticosteroids for the first 2 - 4 weeks of treatment in order to decrease swelling, redness, and pain quickly. Then, after a few weeks of corticosteroid treatment, patients will begin taking an isotretinoin dosage of 0.5 - 1 milligram/kilogram/day, usually for 4 - 5 months. The combination of corticosteroids and isotretinoin is highly effective at clearing acne cysts, but it is a serious decision, as it comes with severe side effects, some of which may be lifelong. These side effects include permanent changes to the body and dramatic birth defects or fetal death if taken by pregnant women.
  3. Oral antibiotics: Oral antibiotics, including tetracycline, minocycline, and doxycycline, are alternatives to isotretinoin that can temporarily help clear acne cysts. Oral antibiotics should only be used for a maximum of 3 - 6 months, and although they may help reduce acne cysts during treatment, the acne will likely return once the treatment is stopped. Further, oral antibiotics cause side effects, including gastrointestinal issues, and can permanently stain the teeth or skin. Oral antibiotics should never be taken with isotretinoin because there is a risk of developing a disease called pseudotumor cerebri, which causes a buildup of pressure inside the skull. Oral antibiotics are also sometimes prescribed alongside draining sinuses treatments to prevent the development of infections inside the draining sinus.
  4. Hormonal treatments (females): Hormonal treatments, including oral contraceptives and spironolactone, are treatments female patients can use to treat acne cysts. These treatments can only be used by females since they can cause feminization symptoms, including breast growth and sexual dysfunction, in men. In females, though, hormonal treatments can be highly effective at clearing acne cysts.4-6


  1. Jansen, T., Lindner, A. & Plewig, G. Draining sinus in acne and rosacea. A clinical, histopathologic and experimental study. Hautarzt 46, 417 - 420 (1995) https://www.ncbi.nlm.nih.gov/pubmed/7642386
  2. Anderson, B., Netter, F. & Machado, C. THE NETTER COLLECTION of Medical Illustrations. (Elsevier Saunders, 2012) https://www.elsevier.com/books/the-netter-collection-of-medical-illustrations-integumentary-system/anderson/978-1-4377-5654-8
  3. Jansen, T., Romiti, R., Plewig, G. & Altmeyer, P. Disfiguring Draining Sinus Tracts in a Female Acne Patient. Pediatr Dermatol 17, 123 - 125 (2000). https://www.ncbi.nlm.nih.gov/pubmed/10792801
  4. Schwartz, R. Acne Conglobata Treatment & Management: Medical Care, Surgical Care, Consultations. Emedicine.medscape.com (2016). http://emedicine.medscape.com/article/1072716-treatment
  5. Habif, T. P. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 231 - 233 (2016). https://www.elsevier.com/books/clinical-dermatology/habif/978-0-323-26183-8
  6. Arndt, K. Manual of Dermatologic Therapeutics (7th Edition). 5 - 8 (LWW (PE), 2007).

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