Table of Contents >> Show >> Hide
- Why Crohn’s can show up on your skin
- The most common Crohn’s-related skin eruptions (and how they look)
- Crohn’s “skin issues” that are really perianal disease (and yes, they count)
- Less common (but important) Crohn’s-associated rashes
- Could it be your Crohn’s medication instead?
- A quick “how it looks” cheat sheet
- What doctors usually do to confirm what it is
- When to call your doctor right away
- Conclusion
- Experiences: what Crohn’s-related skin flares can feel like in real life
- The “my shins feel bruised, but I didn’t do anything” week
- The “it started as a tiny spot… and then it got angry fast” spiral
- The “mystery rash after a new medication” detective story
- The “perianal problems nobody wants to talk about” reality
- The “I feel dismissed because it’s ‘just skin’” frustration
Crohn’s disease is famous for gut dramacramps, diarrhea, fatigue, the whole plotline. But Crohn’s can also be a “multitalented” condition that
auditions for roles outside your intestines. One of its favorite side gigs? Skin problems.
If you’ve ever looked down at your legs (or around your waistband, orawkwardlyaround your butt) and thought, “Is my skin trying to tell me
something?” you’re not being paranoid. Skin changes can be an extraintestinal manifestation of inflammatory bowel disease (IBD), and they can show up
before, during, or after a digestive flare. In some people, the skin is the first place the immune system chooses to complain. In others, it’s a
not-so-subtle sign that inflammation is active somewhere else.
This guide breaks down what Crohn’s-related rashes and lesions commonly look like, where they tend to appear, what they feel like, and what usually
helps. It’s not a substitute for medical carebut it can help you describe what you’re seeing (and decide when to call your gastroenterologist or a
dermatologist).
Why Crohn’s can show up on your skin
Crohn’s is an immune-mediated inflammatory disease. Your immune system, which is supposed to protect you, sometimes stays in “high alert” mode and
triggers inflammation that doesn’t limit itself to the digestive tract. The skin is a common place for these extraintestinal symptoms to land.
Skin issues in Crohn’s generally fall into a few buckets:
- Inflammation-linked rashes that track with bowel activity (often improving when Crohn’s is controlled).
- Neutrophilic dermatoses (immune-driven conditions where certain white blood cells pile into the skin and cause painful lesions).
- “Direct” Crohn’s skin disease (rare, but Crohn’s-type inflammation can occur on the skin itself).
- Nutrient-related changes from malabsorption or chronic inflammation (for example, some deficiencies can affect skin integrity).
- Medication reactions (allergies, injection-site reactions, or paradoxical skin conditions triggered by certain therapies).
Translation: your skin can be a messenger. Sometimes it’s delivering a helpful memo. Sometimes it’s sending a dramatic voicemail at 2 a.m.
The most common Crohn’s-related skin eruptions (and how they look)
1) Erythema nodosum: tender “bruise-like” bumps under the skin
How it looks: Erythema nodosum usually shows up as round or oval, tender red lumps under the skin. They often look like raised
bruises or deep knots, and they can shift from bright red to a purplish, bruise-like color over several days.
Where it shows up: Most commonly on the fronts of the shins. It can also appear on ankles, calves, thighs, or arms.
How it feels: Painful and sore to the touchsometimes warm. People often describe it as “my legs hurt even when nothing is
touching them.” It can come with fatigue, fever, or achy joints.
When it happens: Often during a flare or just before one. It may improve as intestinal inflammation is treated.
What helps: Managing the underlying Crohn’s is the big lever. Supportive measures like rest and elevating the legs may help with
discomfort. Because some pain relievers can worsen IBD for certain people, it’s smart to ask your GI team before you “NSAID your way through it.”
Red flag: If one spot becomes intensely hot, rapidly enlarges, or you develop high feverget checked. Not everything that’s red is
“just inflammation,” and infection needs to be ruled out.
2) Pyoderma gangrenosum: a painful ulcer with a dramatic purple border
How it looks: Pyoderma gangrenosum (PG) often starts smalllike a pimple, pustule, or blister. Then it can expand quickly into an
open sore (ulcer). Classic PG ulcers are typically very painful and can have distinct raised edges that look purple, blue, or dusky compared with the
surrounding skin.
Where it shows up: Most often on the legs, especially the lower legs, but it can appear on arms, trunk, or around surgical sites or
stomas (if you have one).
How it feels: Pain is the headline symptom. The area may feel extremely tender, swollen, and inflamedsometimes far out of
proportion to how “small” it looked at the beginning.
Why it’s tricky: PG can resemble an infection, but it isn’t caused by bacteria. That said, ulcers can become secondarily infected, so
clinicians often evaluate carefully before deciding on treatment. Also, PG can worsen after minor trauma (a phenomenon called pathergy), which is one
reason aggressive “picking at it” or unnecessary procedures can backfire.
What helps: PG is usually treated with medical therapy that calms the immune response, plus careful wound care and pain management.
Because it can progress quickly, this is not a “wait and see for three weeks” situationcall your care team promptly.
Red flag: A rapidly expanding, very painful ulcerespecially with fever or spreading rednessneeds urgent evaluation.
3) Mouth sores (aphthous ulcers): not “skin,” but still a Crohn’s clue
Your mouth is basically the opening chapter of your digestive tract, so it’s not shocking that Crohn’s sometimes leaves notes there too.
How it looks: Small, shallow ulcers inside the mouthoften with a pale or whitish center and a red rim. They may appear on the inner
lips, cheeks, gums, or tongue.
How it feels: Burning or stinging, especially with spicy, acidic, or hot foods. Sometimes they show up during flares.
What helps: Treating intestinal inflammation can help reduce recurrence. Topical treatments (like certain mouth rinses or gels) are
often used for comfort, depending on severityyour clinician can guide you.
Crohn’s “skin issues” that are really perianal disease (and yes, they count)
A lot of Crohn’s-related skin frustration happens around the anus and perineum. This isn’t always a rash in the classic sense, but it’s absolutely a
skin problemand it can be one of the most disruptive.
Perianal skin tags
How they look: Soft folds or “extra” pieces of skin around the anus. In Crohn’s, skin tags can be swollen or more prominent due to
chronic inflammation. They may trap moisture or stool and become irritated.
What to know: Many people assume skin tags are purely cosmetic and try to remove them. With Crohn’s, removal can be complicated,
especially if there is active inflammationso this is something to discuss with specialists rather than a DIY project.
Anal fissures, abscesses, fistulas
How they look/feel: Fissures are tiny tears that can sting or bleed, especially with bowel movements. Abscesses can show up as a
tender, hot lump near the anus (often with fever). Fistulas may cause drainage, pain, or recurring infections.
Bottom line: If you have persistent perianal pain, drainage, fever, or swellingdon’t tough it out in silence. Perianal Crohn’s is
common enough that many GI and colorectal teams have clear pathways to evaluate and treat it.
Less common (but important) Crohn’s-associated rashes
Some Crohn’s-related skin conditions are rarer, but they matter because they can be intense, confusing, or easily mistaken for other diseases.
Sweet syndrome: tender red plaques plus fever
How it looks: A sudden eruption of painful, tender red or reddish-purple bumps or raised patches (plaques). They can appear on arms,
legs, trunk, face, or neck.
How it feels: Often comes with fever and a general “I got hit by a truck” feeling. Because it’s rare and can resemble infection or an
allergic reaction, it often needs clinical evaluationand sometimes a biopsyto confirm.
BADAS (bowel-associated dermatosis-arthritis syndrome): bumps, pustules, and joint pain
How it looks: Recurrent outbreaks of small, sometimes pus-filled lesions (often described as vesicles or pustules) along with flu-like
symptoms and joint pain.
Why it’s confusing: It’s rare, and it can look like other inflammatory skin diseases. The “arthritis” piece (achy, swollen joints)
can be an important clue when it appears alongside skin eruptions in someone with bowel disease.
Cutaneous (metastatic) Crohn’s disease: Crohn’s inflammation on the skin itself
How it looks: This is uncommon, but it’s a real entity. Lesions can varyplaques, nodules, ulcers, or swollen areas. They may appear
in skin folds, the genital region, or on limbs, and they are not necessarily connected to a fistula or nearby bowel disease.
How it’s diagnosed: A dermatologist may recommend a skin biopsy to look for characteristic inflammatory changes. Treatment often
overlaps with Crohn’s treatment because the underlying driver is immune inflammation.
Could it be your Crohn’s medication instead?
Medications that treat Crohn’s can sometimes cause skin reactions. That doesn’t mean you should stop treatment on your ownmany reactions are manageable
and your care team can help adjust therapy safely.
Common medication-related patterns
- Injection-site reactions: redness, itching, swelling, or rash where the shot went in (often mild, sometimes annoying).
- Allergic reactions: hives, widespread itchy rash, facial swelling, or trouble breathing (this can be an emergencyseek urgent care).
-
“Paradoxical” rashes: in some people, certain biologics can trigger psoriasis-like plaques or eczema-like dermatitis even while they
improve the gut. Dermatology can often treat the skin while GI manages the Crohn’s plan.
If you notice a new rash soon after starting or changing a medication, take clear photos, note the timing, and contact your clinician. Timing is a
huge diagnostic clue.
A quick “how it looks” cheat sheet
If you’re trying to describe a Crohn’s-related skin issue quickly, these snapshots can help:
- Tender red lumps that turn bruise-like on the shins → often erythema nodosum.
-
A small blister/pustule that becomes a fast-growing, very painful ulcer with purple/blue edges → possible pyoderma gangrenosum (get
evaluated urgently). - Sudden painful red plaques with fever → possible Sweet syndrome.
- Recurring small pustules plus joint pain and flu-like symptoms → consider BADAS (needs clinician evaluation).
- Skin tags, fissures, drainage, swelling around the anus → perianal Crohn’s disease patterns.
Skin can look different depending on your skin tone. For example, “redness” may appear more purple, brown, or gray on darker skin, and swelling or
warmth may be more noticeable than color changes. If you’re unsure, describing texture (raised, ulcerated, blistered), pain level, speed of change,
and location can be more useful than color alone.
What doctors usually do to confirm what it is
Crohn’s-related skin issues can mimic infections, allergic reactions, vascular problems, or unrelated dermatologic conditions. Clinicians often combine:
- History: timing with GI symptoms, new meds, recent infections, injuries, or procedures.
- Exam: pattern, location, tenderness, ulcer edges, drainage, and surrounding inflammation.
- Labs: if there’s fever or concern for infection/systemic inflammation.
- Biopsy: sometimes used for confirmation (especially for unusual lesions or suspected cutaneous Crohn’s).
A practical tip: bring photos that show how the lesion started and how quickly it changed. Many skin conditions evolve fast, and your appointment might
land when it looks “different” than it did at peak drama.
When to call your doctor right away
Not every rash is an emergency, but these situations deserve quick attention:
- Rapidly expanding painful ulcers (especially if they started as a small blister/pustule).
- Fever, chills, or feeling severely unwell with a new skin eruption.
- Signs of infection (spreading warmth/redness, pus, escalating pain).
- Allergic reaction signs such as facial swelling, hives, wheezing, trouble breathing, or trouble swallowing.
- Perianal swelling, severe pain, or drainage (possible abscess/fistula).
If you’re on immune-modulating therapy, prompt evaluation matters even more. Some infections can look like inflammatory rashes early on, and it’s
safer to let your team sort it out.
Conclusion
Crohn’s skin eruptions can be confusing, uncomfortable, and occasionally scaryespecially when they appear out of nowhere or look nothing like the
“typical” rash you’d imagine. The good news is that many Crohn’s-related skin issues improve when intestinal inflammation is controlled, and even the
more intense ones (like pyoderma gangrenosum) have treatment pathways when caught early.
If you take one thing from this article, let it be this: the pattern matters. Where the lesions show up, how fast they change, how
painful they are, and whether they match your flare cycle are all clues. Document what you see, then bring your observations to the people who can help
you turn “mystery rash” into a plan.
Experiences: what Crohn’s-related skin flares can feel like in real life
Medical descriptions are useful“tender nodules,” “violaceous border,” “neutrophilic dermatosis”but they don’t always capture the lived experience of
having your skin suddenly act like it joined the Crohn’s group chat. Here are common experience patterns people report, written as realistic composites
(not individual medical advice), to help you recognize the vibe of these conditions.
The “my shins feel bruised, but I didn’t do anything” week
A classic erythema nodosum experience often starts with soreness when walking up stairs, kneeling, or even pulling on socks. Then you notice a few
raised, tender lumps on the front of your shins. They can look like bruises that forgot to mention where they came from. Some people say the bumps
feel warm and painful when touched, and that the discomfort seems deeper than the skinlike the ache is coming from underneath.
What makes it emotionally draining is the timing: it often overlaps with fatigue and gut symptoms. You’re already low on energy, and now your legs
hurt enough that errands feel like a fitness test you didn’t sign up for. A practical coping move many people find helpful is taking photos daily
(color changes can be subtle) and noting whether it improves when Crohn’s treatment is adjusted. That timeline can help your clinician connect the dots.
The “it started as a tiny spot… and then it got angry fast” spiral
Pyoderma gangrenosum experiences tend to be memorablebecause pain and speed are big features. Someone may notice a small bump, blister, or pustule,
sometimes after minor trauma (like shaving, a scratch, or a bump into furniture). Within days, it can expand and break down into a painful open sore.
People often describe the pain as intense and disproportionate, with a raw burning quality that makes it hard to sleep or focus.
The most stressful part is that it can look infected, so you may worry you did something “wrong” or that you waited too long. Many patients describe
relief when a clinician takes it seriously early and coordinates care between dermatology, wound care, and gastroenterology. The day-to-day reality can
involve careful dressing changes, avoiding unnecessary friction, and managing pain while inflammation is brought under control.
The “mystery rash after a new medication” detective story
Starting a new Crohn’s medication can come with an internal monologue like: “Is this normal? Is this dangerous? Is my immune system trying to file a
complaint?” Some people experience mild injection-site reactionsredness, itching, or a small rash where the medication was given. Others develop more
widespread itching or eczema-like patches that seem unrelated to the gut flare itself.
A common experience is uncertainty about what to do next: stop the medication and risk a flare, or continue and risk worsening the rash. In practice,
the safest path is often to contact your care team quickly, share photos, and describe timing (how soon after the dose, how long it lasted, whether it
recurred with the next dose). Many medication-related rashes are treatable without abandoning effective Crohn’s therapyespecially with dermatology
support. But if symptoms include hives, facial swelling, or breathing trouble, people report that urgent care was the right call.
The “perianal problems nobody wants to talk about” reality
Perianal Crohn’s experiences can be uniquely isolating, because the symptoms are both painful and socially awkward. People may notice skin tags that
become irritated, fissures that sting sharply, or drainage that requires pads or frequent hygiene routines. It can affect sitting, walking, intimacy,
exercise, and confidencebasically, all the “normal life” stuff you don’t want Crohn’s to interfere with.
Many people describe a turning point when they finally bring it up directly with a clinician and learn that perianal Crohn’s is commonand treatable.
Practical strategies patients often mention include gentle cleansing (not harsh scrubbing), warm sitz baths as advised, protective barrier ointments,
and having a clear plan for flare symptoms. The biggest emotional relief often comes from not having to improvise in silence.
The “I feel dismissed because it’s ‘just skin’” frustration
A recurring theme in chronic illness communities is that skin symptoms sometimes get minimizeduntil they’re severe. But skin pain can be debilitating,
and visible rashes can affect mental health. Many people report that being specific helps: describing pain level (0–10), speed of spread, whether it’s
ulcerated, whether there’s fever, and whether it correlates with GI symptoms. Bringing a short written timeline (even a few bullet points) can shift the
conversation from “vague rash” to “actionable clinical picture.”
If you’re navigating Crohn’s, you deserve care that treats your whole body, not just your intestines. The skin is part of that storysometimes a
footnote, sometimes a chapter, but never something you have to tough out alone.
