Impetigo is a bacterial skin infection that produces honey-colored crusts, while tinea is a fungal infection that typically forms ring-shaped, scaly patches. Despite both being common, contagious skin conditions that affect the outer layers of skin, they have different causes, look different on the body, and require completely different treatments. Mixing them up can mean weeks of using the wrong medication while the infection spreads.
Different Organisms, Different Infections
Impetigo is caused by bacteria, specifically Staphylococcus aureus, group A Streptococcus, or both acting together. It’s most common in children aged 2 to 5 and spreads easily through direct skin contact or shared items like towels.
Tinea is caused by a group of fungi called dermatophytes. These organisms survive by breaking down keratin, the protein that makes up the outermost layer of your skin, hair, and nails. The most common species responsible include Trichophyton mentagrophytes, Trichophyton rubrum, and Microsporum canis. You might know tinea by its more familiar names: ringworm (on the body), athlete’s foot (on the feet), or jock itch (in the groin).
Both infections stay superficial. Tinea fungi only invade the very top layer of the epidermis (the stratum corneum), along with hair and nails. Impetigo bacteria also target superficial skin, though certain strains of Staphylococcus aureus produce toxins that can split deeper layers of the epidermis by attacking the proteins that hold skin cells together.
How They Look on the Skin
The visual differences between impetigo and tinea are often the fastest way to tell them apart, though the two can occasionally mimic each other.
Impetigo starts as small, itchy sores that burst quickly. The fluid that seeps out is yellow or tan and dries into a distinctive honey-colored crust. The skin around the sores often looks red and raw. In the bullous form, larger fluid-filled blisters appear first, then go limp and break open before crusting over. Both types heal without scarring.
Tinea looks quite different. The hallmark is a ring-shaped patch with a raised, red, scaly border and clearer skin in the center. It tends to expand outward over time. On the feet, it can appear as cracking and peeling between the toes or in a “moccasin” pattern covering the sole. On the scalp, it may cause patchy hair loss. Tinea is typically itchy but rarely produces the oozing, crusty sores characteristic of impetigo.
One reason misdiagnosis happens: a type of fungal infection called impetigo-like tinea can produce pustules and golden crusts that closely resemble bacterial impetigo, particularly on the face in children. This is most often caused by Trichophyton mentagrophytes, a fungus that triggers a stronger inflammatory reaction than other species.
Where Each Infection Shows Up
Impetigo favors the face, particularly around the nose and mouth, and the extremities. It often starts at a site of broken skin, such as a cut, insect bite, or area of eczema, where bacteria can get a foothold.
Tinea has a wider range. On the body (tinea corporis), it develops primarily on exposed skin and the extremities. On the feet (tinea pedis), it thrives in the warm, moist environment created by shoes and socks, and is the most common type overall. Tinea pedis can spread to the groin when fungal spores transfer to undergarments during dressing, leading to tinea cruris. It also affects the scalp and nails, where it can be especially stubborn to clear.
How Each Is Diagnosed
A doctor can often diagnose either condition by examining the skin, but lab tests confirm the diagnosis when the picture isn’t clear.
For tinea, the standard test involves scraping a small sample of skin and examining it under a microscope after treating it with potassium hydroxide (KOH), a solution that dissolves skin cells and makes fungal elements easier to see. This test picks up about 73% of true infections. A fungal culture is more specific but can take up to three weeks to grow. The most definitive diagnosis combines a positive KOH test, a positive culture, and a clinical appearance consistent with tinea.
For impetigo, diagnosis is usually clinical, based on the characteristic honey-colored crusting. When confirmation is needed, a bacterial culture from the wound can identify the exact organism and help guide antibiotic choice, particularly if treatment isn’t working.
Treatment Is Completely Different
This is where getting the diagnosis right matters most. Antibiotics treat impetigo. Antifungals treat tinea. Using the wrong one won’t help and gives the infection more time to spread.
Impetigo is treated with topical antibiotics applied directly to the sores, typically for about seven days. More widespread cases may need oral antibiotics. Most cases resolve within two to three weeks, and even untreated impetigo tends to clear on its own in that timeframe, though treatment speeds healing and reduces the chance of spreading it to others. Children can usually return to school or daycare 24 hours after starting antibiotics, once they’re no longer considered contagious.
Tinea requires antifungal medications. Mild cases on the body, feet, or groin often respond to over-the-counter topical antifungals applied for several weeks. Infections on the scalp or nails, or cases that don’t respond to topical treatment, typically need oral antifungal medication. Treatment timelines vary widely: a simple patch of ringworm on the body might clear in two to four weeks, while a nail infection can take months.
Risks of Leaving Them Untreated
Untreated impetigo carries the more serious potential complications. Because group A Streptococcus is one of the bacteria involved, impetigo can in rare cases lead to post-streptococcal glomerulonephritis, a kidney condition that develops when the immune system’s response to the infection damages the kidneys’ filtering units. Complications are uncommon, but the bacterial nature of impetigo means it can also spread deeper into the skin or enter the bloodstream if ignored.
Untreated tinea is less likely to cause systemic problems, but it won’t go away on its own. It spreads outward on the skin and can jump to new body sites or to other people. Nail infections in particular become progressively harder to treat the longer they go unaddressed, and tinea on the scalp can lead to permanent hair loss if scarring occurs.
Quick Comparison
- Cause: Impetigo is bacterial (Staph and Strep). Tinea is fungal (dermatophytes).
- Appearance: Impetigo produces oozing sores with honey-colored crusts. Tinea forms ring-shaped, scaly patches.
- Common locations: Impetigo clusters around the face and extremities. Tinea appears on the body, feet, groin, scalp, and nails.
- Treatment: Impetigo responds to antibiotics. Tinea requires antifungals.
- Healing time: Impetigo typically resolves in two to three weeks. Tinea ranges from weeks to months depending on the site.
- Contagion after treatment: Impetigo is generally no longer contagious 24 hours after starting antibiotics. Tinea remains contagious until treatment is well underway, often 48 to 72 hours or longer.