If a small bump appears in an unexpected part of your body — maybe under your arm or along your inner thigh — you might first assume it’s a pimple. But if the lump persists for weeks and becomes painful and swollen, it may indicate hidradenitis suppurativa (HS). This chronic (lifelong) skin condition, which is also called acne inversa, often starts with symptoms like these.

Understanding how HS looks, what triggers flare-ups, and how to manage symptoms can help you find relief and better manage your health. Read on to learn more about seven symptoms of HS.

1. Blackheads

The first sign of hidradenitis suppurativa might look like harmless blackheads. These small bumps, also known as comedones, often appear in pairs that may be easy to overlook or mistake for a common skin issue such as acne.

Hidradenitis suppurativa commonly affects areas of the body with apocrine sweat glands or hair follicles, especially where there’s frequent friction and sweating. Blackheads associated with HS often appear in places like the inner thighs, axillae (armpits), or under the breasts. Bumps that look like pimples but don’t seem quite like typical acne could be an early symptom of HS.

HS also tends to show up in these areas:

• Groin and genitals
• Between the buttocks
• Neck
• Scalp
• Back
• Abdomen or waist

2. Painful Lumps

As hidradenitis suppurativa progresses, blackheads can turn into tender, swollen, painful lumps or nodules, which are a hallmark of HS. Unlike boils or pimples, nodules may persist for weeks or months.

3. Abscesses

Nodules may progress into abscesses — pus-filled lesions that develop as painful lumps grow larger and more inflamed. Abscesses are painful and can make movement difficult. If an abscess bursts, it may release foul-smelling pus.

Abscesses can form anywhere you have HS symptoms and may linger for weeks or even months. If they burst, they can take a long time to heal, sometimes leading to further complications like scarring or secondary infection.

4. Sinus Tracts

In severe hidradenitis suppurativa, sinus tracts — also known as tunnels — can form under the skin. Tunnels connect different lesions, often creating complex networks beneath the surface. They can drain pus, become inflamed, and lead to more abscesses and greater pain.

Sinus tracts are a symptom of HS progression to a more serious stage. Tunnels form after repeated abscesses affect the same area. Sinus tracts can be a significant source of pain and may leave scars.

5. Scarring

Repeated inflammation, abscesses, and sinus tracts in HS often lead to scarring. As lesions heal, they leave thickened, raised or pitted areas of skin that are often darkened and firm to the touch. Scars involving sinus tracts can become especially pronounced. Fibrous tissue from repeated inflammation can build up and limit flexibility and movement.

Scarring can be one of the most challenging aspects of HS. Scars may reduce the skin’s elasticity, causing tightness, discomfort, and restricted movement, and may also lead to self-consciousness for some individuals.

6. Pain

One of the most persistent symptoms of hidradenitis suppurativa is pain, which can make it difficult to move freely, especially in areas where skin rubs against skin or clothing.

With mild HS, pain may develop only during flare-ups. However, people with more severe HS symptoms may experience chronic pain that significantly affects daily life, making ordinary activities — like lifting your arms, sitting, or walking — uncomfortable or difficult. Untreated pain can lead to limited mobility.

7. Mental Health Symptoms

Managing chronic pain, persistent abscesses, and visible scars can take a toll on mental health and affect quality of life. Flares can be unpredictable and disruptive, and people with HS may feel anxious about when the next flare-up will come.

The emotional aspects of HS can lead to depression, anxiety, and feelings of isolation. You may be concerned about visible scars, odor from draining abscesses, or pain with everyday movements. The condition’s effect on mental health can be as significant as the physical symptoms, so it’s important to manage stress with HS. Be sure to talk with your health care provider to get the support you need and a treatment plan that addresses all your HS symptoms, both mental and physical.

Triggers of Hidradenitis Suppurativa Flares

HS flare-ups can happen suddenly, and it helps to know what might be causing them. Common triggers include:

• Hormonal changes — Symptoms may get worse around menstruation, which suggests a link between hormone levels and flare severity.
• Stress — Both physical and emotional stress can trigger an HS flare-up. Everyday stresses such as work or personal events can make symptoms worse.
• Heat and sweating — Excessive heat and sweating can also trigger HS, particularly where skin rubs together. HS symptoms tend to get worse in hot, humid conditions.
• Dietary factors — Certain foods, such as those containing dairy, sugar, or brewer’s yeast, can set off HS symptoms in some people.
• Scented skin products — Results of a small survey suggested that the chemicals in skin products like deodorants and antiperspirants, especially roll-on and stick versions, can worsen symptoms in some people with HS.
• Smoking — People who smoke tend to have more areas affected by HS than those who don’t smoke. If you smoke, quitting might help you manage your symptoms and flare-ups.

People with obesity (a body mass index score of over 30) also are more likely to have symptoms of HS. However, it’s important to note that having a high body weight doesn’t cause HS, and losing weight won’t cure it.

How To Avoid an HS Flare-Up

HS flares can be challenging to manage, but you can take steps to lower their impact. Wearing loose-fitting clothes that don’t irritate your skin, reducing stress, and staying cool in hot weather can all help prevent flare-ups. Some people find it helpful to avoid known dietary triggers.

For some people with HS, a diet rich in anti-inflammatory foods may lead to fewer and milder flare-ups. Berries, leafy greens, tomatoes, and other colorful produce are packed with antioxidants that fight inflammation. Omega-3 fatty acids found in fatty fish, walnuts, chia seeds, and flaxseed can help reduce inflammation. The spices turmeric and ginger also have strong anti-inflammatory properties and may help reduce symptoms. However, researchers haven’t fully established the benefits of specific foods in HS.

If your flare-ups are frequent and severe, speak with a health care provider about treatments for HS. They may recommend medications like antibiotics (oral or topical), biologic drugs, anti-inflammatory agents, corticosteroids, or retinoids. Surgical procedures might also be recommended for some cases.

Talk With Others Who Understand

On myHSteam, the social network for people with hidradenitis suppurativa, more than 44,000 members come together to ask questions, give advice, and share their stories with others who understand life with HS.

Have you been diagnosed with HS? What symptoms are you experiencing, and how do you manage them? Share your thoughts in the comments below, or start a conversation by posting on your Activities page.