What should you know about plantar cellulitis?

Plantar cellulitis is a bacterial infection of deeper skin on the sole or foot that needs prompt medical assessment and treatment. It may begin through a crack, blister, puncture, cut, insect bite or fungal infection between the toes. The sole can be difficult to inspect, especially when swelling or tenderness makes walking uncomfortable. A clinician may need to examine the whole foot, including the spaces between the toes, to look for an entry point and check whether the infection is spreading.

Cellulitis often causes a warm, tender, swollen area of skin with redness that may expand over time. On the plantar surface, redness can be less obvious because the skin is thicker; pain, heat, swelling and difficulty bearing weight may be more noticeable. The infection can involve the top of the foot, heel, toes or tissues around a wound as well as the sole. Chills, fever or feeling generally unwell can occur when the body is responding to infection. Most people with cellulitis notice local skin pain, redness or swelling, but these symptoms can also have other causes.

Athlete's foot can create peeling or fissured skin that gives bacteria a route into deeper tissue. A puncture wound may be small on the surface while extending further below it, so tell the clinician about stepping on an object, a recent blister, nail problem or foot procedure. Type 2 diabetes, reduced circulation, nerve damage or a weakened immune system can make foot infections more complicated and should be mentioned during assessment.

Arrange prompt medical assessment rather than waiting for the redness or pain to settle. Treatment commonly involves an antibiotic chosen for the suspected bacteria and the severity and location of the infection. Take it exactly as prescribed and complete the course unless the prescriber changes the plan. Keep any wound clean and covered, avoid squeezing or puncturing the area, and reduce pressure on the foot. Elevating the foot when resting can help limit swelling. Marking the edge of visible redness can help show whether it is extending, but it does not replace review.

Do not use leftover antibiotics or share medication. A clinician may need to drain a collection of pus, remove damaged tissue, check for a retained foreign body or arrange further tests when a puncture wound, deep pain or poor response raises concern. Seek reassessment if symptoms continue to worsen or do not begin improving after treatment starts.

Seek urgent medical help for rapidly spreading redness or swelling, severe or escalating pain, red streaks moving up the foot or leg, numbness, skin colour changes, blisters, blackened skin, pus, or inability to walk. Get emergency help if fever comes with confusion, faintness, extreme weakness, fast breathing, a racing heartbeat or difficulty staying awake. These features can signal a serious infection or sepsis. People with diabetes, poor circulation, loss of sensation in the feet or immune suppression should seek same-day advice for a new wound or suspected infection, even when the skin changes seem limited.

You could ask: Where is the infection starting, and is there a wound, fungal infection or collection that needs separate treatment? Which changes should improve first? How should I protect the foot while it heals? Do my diabetes, circulation, medicines or allergies alter the treatment plan? What should I do if the redness, swelling, pain or fever worsens?