Contact dermatitis is a rash caused by something that touched the skin. It comes in two forms - irritation from a substance that would bother anyone given enough exposure, and an allergic reaction to something only some people react to. Both clear once the cause is found and removed. Cellulitis is a bacterial infection of the deeper layers of the skin and the fat underneath. The area becomes swollen, warm, tender and discolored, and it spreads. It needs antibiotics, and some presentations need care the same day.
The same eight facts on every condition comparison.
It is eczema from contact.
A substance touching the skin provokes the rash.
There are two types.
Irritant dermatitis damages the barrier directly; allergic dermatitis is a delayed immune reaction.
Patch testing finds allergies.
It differs from skin-prick testing.
The exposure is part of treatment.
Identifying what touched the skin guides care.
It is a bacterial skin infection.
Bacteria enter through a crack or wound, sometimes too small to notice.
It affects deeper skin layers.
Inflammation in the dermis and fat causes warmth, tenderness and swelling.
Lookalikes are common.
Dermatitis and venous inflammation can appear similar.
Diagnosis is mainly clinical.
Tests are used selectively; a swollen leg may also need a clot check.
Irritant contact dermatitis Damage from soaps, solvents or water; most common.
Allergic contact dermatitis Immune reaction to nickel, fragrance, plants and more.
Swollen leg Warm, tender, one-sided swelling.
Spreading area Enlarges over hours to days.
Entry point Often a cut or cracked skin.
Skin contact can cause inflammation through direct irritation or a delayed allergic reaction. These are different routes to a rash that may itch, swell, blister or scale.
Bacteria enter through a break in the barrier and infect deeper skin and nearby tissue. The inflammatory response causes warmth, swelling, tenderness and an area that may expand.
Contact Dermatitis. Can begin at any age after irritation or sensitization to a contacting substance.
Cellulitis. Can develop at any age when bacteria enter deeper skin, often through a break in the barrier.
Contact dermatitis happens when something touching the skin either damages it directly or sets off an allergic reaction. The rash shows up where the contact happened.
Cellulitis is a bacterial infection, usually from strep or staph, that gets into the deeper skin through a break.
People with eczema or a family history of allergies react more easily.
Evidence labels come from each condition’s own treatment list.
The mildest topical steroid, and enough for a small patch on the body once the contact has stopped. Use it twice a day for one to two weeks rather than dabbing it on now and then. It is often too weak for the hands or feet, and on the face or eyelids it should be short-term and worth asking about first.
Contact dermatitis is not driven by histamine, so antihistamines do very little for the rash itself. A sedating one at night can help you sleep through the itching instead of scratching, which is worth something. The non-drowsy daytime ones sold for hay fever will not make much difference here.
Worth naming because they are so often reached for. Neomycin and bacitracin are among the most common contact allergens there are, so an ointment used on an itchy rash can become the reason the rash will not go. Unless the skin is genuinely infected, plain petroleum jelly does the same job with none of the risk.
Plain petroleum jelly, or any thick fragrance-free ointment, rebuilds the barrier that irritation broke. Barrier repair is genuinely half the treatment in irritant hand dermatitis, and it works because it has no fragrance, preservative or botanical in it to start a second reaction. Apply after every hand wash, not once a day.
An oatmeal bath can take the edge off the itch of a widespread reaction, in cool rather than hot water. It is comfort only. Pick a plain one, because an itch product with fragrance or botanicals in it is a common way people acquire a second allergy on top of the first.
These cover the pain and bring the fever down while the antibiotics do the work. Taking them regularly for the first couple of days works better than waiting for the pain to peak. They do not treat the infection, and pain that is far worse than the skin looks is a reason to be seen urgently rather than to take more.
Athlete's foot between the toes is the most commonly identified way bacteria get into a leg, and it is one of the few entry points you can genuinely close. An antifungal cream used on the toe webs for two to four weeks, and repeated whenever the skin cracks again, lowers the chance of another episode. It does nothing for the infection you have today.
Cellulitis sits below the surface, deeper than any cream reaches, so an over-the-counter antibiotic ointment cannot treat it. Using one and watching for a day is a common reason people arrive later than they should. It is reasonable on a small fresh cut to keep it clean, and that is all.
A mid-strength steroid cream or ointment, the usual prescription for contact dermatitis on the body, arms or legs. Two weeks of it will clear most reactions once the contact has stopped. It is too strong for the eyelids and the folds, and it is a treatment for the inflammation, not for the cause.
Clobetasol Propionate. A potent steroid ointment for hands and feet, where the skin is thick enough that milder creams barely register. It is used in short bursts of two to three weeks with breaks in between, not continuously. Nothing above the neck, and remember that hand dermatitis takes six weeks or more to settle even when the steroid is doing its job.
A non-steroid ointment for the eyelids, face and skin folds, where repeated steroid use thins the skin. It calms the same immune reaction without that risk, which makes it useful for eyelid dermatitis that keeps returning while the trigger is being tracked down. It stings for the first few days, and that usually passes.
A mild steroid stronger than over-the-counter hydrocortisone but gentle enough for the face and eyelids in short courses. It is the usual first prescription when a reaction has landed above the neck. Use it for the days it is prescribed for, not as something kept in the drawer.
A gentler alternative to tacrolimus for the face and eyelids, and easier to tolerate for people who cannot get past the initial burning. It is not strong enough for hand dermatitis. Like tacrolimus, it buys comfort while the actual trigger is being identified.
Useful only for the small crusted sore or infected wound that let the bacteria in, not for the cellulitis itself, which is far too deep for a cream to reach. Treating the entry point matters, but it happens alongside antibiotic tablets, never instead of them.
Steroid tablets for a widespread, blistering reaction, most often poison ivy covering large areas or a rash on the face that is closing an eye. The course has to run two to three weeks with a taper; the short packs are the usual reason the rash rebounds a few days after finishing. It is for the big reactions only, not for a patch on one arm.
A short specialist course for severe hand dermatitis that has not responded to strong steroids and proper avoidance. It works quickly and reliably, which is exactly why it is used for a few months rather than long term — blood pressure and kidney function have to be watched throughout. It is a bridge, not an answer.
A weekly tablet sometimes used for chronic hand dermatitis when avoidance and creams have genuinely failed. The evidence in contact dermatitis specifically is thin, mostly borrowed from eczema. It needs regular blood tests, and it is a specialist decision rather than a next step.
Used only when bacteria have moved into the broken skin — spreading warmth and pain, pus, or fever. They treat the infection sitting on top and do nothing to the dermatitis underneath, so the steroid and the avoidance carry on alongside them.
The usual first choice for ordinary cellulitis, taken four times a day for about five to seven days. It covers the streptococci behind most cases and many staph as well. Antibiotics are not optional here - there is no version of cellulitis that clears without them - and the course is finished even though you feel better in two days.
Used when MRSA is a concern, when there is pus or a boil involved, or when penicillins do not suit. It is often paired with a second antibiotic because it covers strep less reliably on its own. It is avoided in pregnancy and in young children, and it makes sunburn more likely.
The other main option when MRSA is suspected, particularly with an abscess or a draining wound. Like doxycycline it is often combined with an antibiotic that covers strep properly. It needs care with kidney problems and with some other medicines, so tell the prescriber everything you take.
An alternative for a genuine penicillin allergy, and it covers both strep and most staph. It causes diarrhoea more often than the others and carries a higher risk of a bowel infection called C. difficile, so it is usually not the first pick. Report diarrhoea that starts during or after the course.
For people who keep getting episodes, a small daily dose of penicillin taken for months roughly halves how often they come back. The effect fades once it is stopped, so it works best alongside compression and treating the entry point. Ask about it if you have had two or more episodes.
An injected biologic increasingly asked about for chronic hand dermatitis. Reports are encouraging for the eczema-like cases, but it is not approved for allergic contact dermatitis and some allergens appear not to respond to it. It does not replace finding and removing the trigger, and it is a specialist conversation.
Timing is the best clue to which form you have. The rash is temporary; the allergy is not - sensitization is generally lifelong, so avoidance is permanent. Once the substance is named and avoided, most people stay clear.
Cellulitis needs prompt antibiotic treatment. Symptoms should begin improving within two to three days, although skin changes can take longer to settle. Worsening symptoms or failure to improve needs reassessment; swelling and repeat episodes can occur.
Infection in the broken skin
Weeping, cracked or scratched skin gives bacteria an opening, most often on the hands. The signs are honey-colored crusts, pus, increasing pain, or redness and warmth spreading outward. It is common and it is treatable, but it needs antibiotics rather than more steroid cream, so it is worth being seen rather than waiting it out.
Chronic hand dermatitis
When the exposure carries on, hand dermatitis stops settling between flares. The skin thickens, the normal lines deepen, and painful cracks open across the fingertips and knuckles that catch on everything and are slow to close. It is the reason contact dermatitis is a leading work-related skin problem, and it is largely preventable by naming the cause early instead of treating the rash for months.
Time off work
Hand dermatitis is one of the leading work-related health problems, and for people in wet or chemical work it can mean weeks of light duties, a change of role, or leaving a trade. It is also the part most often left out of the conversation. Naming the cause early, and getting the right gloves and routine in place, is what keeps the job.
An abscess underneath
A pocket of pus can form inside the infected area, most often when Staphylococcus aureus is involved or there was a boil or wound to begin with. It shows up as a tender lump that feels boggy or fluid-filled, and it is a common reason antibiotics alone are not working at 48 hours. Pus has to be drained as well as treated, so this is a reason to go back rather than wait.
Swelling and repeat episodes
Each episode damages the lymph channels that drain the limb, so the limb swells more afterwards, and a limb that swells is more likely to be infected again. A previous episode is the strongest predictor of the next one. Compression, daily moisturizer and treating athlete's foot break the loop better than any antibiotic does.
Sepsis
The infection can reach the bloodstream and affect the whole body. The signs are a high fever with shaking chills, confusion or new drowsiness, a racing heart, fast breathing, feeling faint, or passing very little urine. It is uncommon but it is time-critical, so it is an emergency department problem rather than a next-day appointment.
Seek help for persistent or recurrent rash; patch testing may identify contact allergy. Pain, spreading warmth, pus or fever require prompt assessment.
Suspected cellulitis needs prompt medical assessment. Rapid spread, severe pain, fever, confusion or infection near the eye warrants urgent care.
Start with location and shape, not a list of products. Photograph the rash, note where its edges are, and look for an object or habit that matches that outline. An allergic reaction shows up one to three days after contact, so look at what happened two days before, not that morning. Include things you have used for years - those are the likeliest candidates, not the least. If a few weeks of attention does not settle it, patch testing ends the guessing.
An irritant reaction improves within days of contact stopping. An allergic reaction takes two to four weeks to settle even with treatment, because the immune cells doing the damage take that long to stand down. Hands are slowest, often six weeks or more, because the skin there is used and washed constantly. Judging it at day three tells you very little.
No. This is your own skin reacting to a substance, not an infection. You cannot pass it on by touch. If two people in a household get the same rash, they were both exposed to the same thing.
Generally no. Once your immune system has learned a substance, that memory is permanent, and tiny amounts can trigger a reaction years later. In practice it is less grim than it sounds - people who know their allergen and avoid it stay clear indefinitely, and the avoidance is usually narrower than they feared.
Eyelid skin is the thinnest on your body, so it reacts to amounts the rest of your skin ignores. Nail polish, hair products, face creams and airborne particles reach the eyelids from your hands or from your scalp. When a rash is on the eyelids alone, the cause is usually somewhere else.
For a small, mild patch on the body, often yes, alongside stopping the contact. Over-the-counter hydrocortisone is a mild strength and rarely clears thicker skin on hands or feet. On the face and eyelids keep it short-term, and ask first. It treats the inflammation, not the cause - if the rash returns each time you stop, find the trigger.
No. The bacteria already live on normal skin, and the infection is in your own deeper tissue. You cannot pass it on, and there is no need to isolate from family. Keep any open, draining wound covered - ordinary wound care.
Common in the first 24 to 48 hours. Dying bacteria release material that briefly intensifies the immune reaction, so the area can look more inflamed while you improve. Watch how you feel, whether the fever settles, and whether the marked edge stops. If it is still spreading at 48 hours, go back.
You should feel better within one to two days, and a typical antibiotic course runs about 5 to 7 days. The skin takes one to two weeks to settle, and peeling is normal. Some swelling and a darker or lighter mark can persist for weeks to months, especially on deeper skin tones.
Most cellulitis is treated with tablets at home. Antibiotics into a vein are used when it is severe or spreading fast, with a high fever or signs of sepsis, when the face or around the eye is involved, when tablets have failed, or with diabetes, poor circulation or a weakened immune system.
Usually because the limb still swells and the entry point was never closed. Long-term leg swelling, untreated athlete's foot, and lymph drainage damaged by a previous episode all make the next one more likely. Compression, moisturizing and treating the foot fungus do more than any antibiotic. If it keeps happening, ask about long-term preventive antibiotics.
No, and the similar names cause a lot of confusion. Cellulite is dimpled normal fat beneath the skin, a cosmetic matter. Cellulitis is a bacterial infection of the deeper skin that needs antibiotics and sometimes urgent care.
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