Dozens of conditions can cause red spots on the skin, ranging from a mild allergic reaction that clears in hours to a serious infection that needs emergency care. The most common culprits are viral infections, chronic inflammatory skin conditions like eczema and psoriasis, allergic hives, and bleeding under the skin from broken blood vessels. Figuring out which one you’re dealing with comes down to a few key details: what the spots look like, where they are, how long they last, and whether you have other symptoms.
Viral Infections
Viruses are one of the most frequent causes of widespread red spots, especially in children. The rash that accompanies a viral illness is called an exanthem, and it typically shows up alongside symptoms like fever, body aches, sore throat, fatigue, or loss of appetite. The spots usually appear suddenly and spread across large areas of the body.
Common viruses that trigger this kind of rash include chickenpox, measles, rubella, roseola, fifth disease (caused by parvovirus B19), and hand, foot and mouth disease. COVID-19, mononucleosis, hepatitis, and HIV can also produce skin rashes, though the pattern varies. Bacterial infections occasionally cause similar rashes, as can reactions to medications.
Hand, foot and mouth disease has a distinctive pattern worth knowing. It starts as small red spots on the tongue and inside the mouth that blister and become painful. A rash then appears on the palms, soles of the feet, buttocks, legs, and arms. The spots are flat or slightly raised, sometimes with blisters surrounded by a red base, and they’re usually not itchy.
Hives From Allergic Reactions
Hives are raised, itchy welts that can appear anywhere on the body. They range from the size of a pencil eraser to as large as a dinner plate. On lighter skin they’re typically red; on darker skin they may be skin-toned or harder to see. A defining feature of hives is that individual welts last no more than 24 hours in one spot, even though new ones may keep popping up elsewhere.
Triggers include foods, medications, insect stings, infections, emotional or physical stress, temperature extremes, exercise, and pressure or scratching on the skin. Most cases of hives resolve on their own or with antihistamines. If hives appear with swelling of the lips, tongue, or throat, or with difficulty breathing, that signals anaphylaxis, which is a medical emergency.
Eczema and Other Inflammatory Conditions
Atopic dermatitis, the most common form of eczema, causes patches of dry, cracked, scaly skin that are intensely itchy. On lighter skin, these patches tend to look red and weepy with crusting. On brown or Black skin, the patches may appear darker or lighter than the surrounding area, and small raised bumps are more typical than flat red patches. Eczema in adults often shows up in areas prone to friction or sweat, like the insides of elbows, behind the knees, and on the hands.
Psoriasis produces thick, scaly plaques that are often silvery-white on top and red or inflamed at the base. Rosacea causes persistent redness and sometimes small bumps across the cheeks, nose, and forehead. Both are chronic conditions that flare and improve in cycles, and they’re often confused with other causes of red spots because they share some visual overlap.
The Butterfly Rash of Lupus
Lupus, an autoimmune disease, can cause a distinctive facial rash that spreads across both cheeks and the bridge of the nose in a butterfly shape. This rash, called a malar rash, spares the laugh lines that run from the sides of the nose to the mouth. On light skin it appears red or pink; on dark skin it may look brown, black, or purple. It can be flat, raised, or scaly, and in rare cases extends to the forehead and chin.
The butterfly rash isn’t the only skin sign of lupus, but it’s one of the most recognizable. It often appears or worsens after sun exposure and may accompany joint pain, fatigue, and other systemic symptoms.
Lyme Disease and the Bullseye Rash
Lyme disease produces a rash called erythema migrans in over 70% of people who are infected. It’s a circular, expanding rash that often develops a target-like or bullseye appearance. It typically shows up at the site of the tick bite, commonly on the chest, back of the knee, or trunk, and gradually grows larger over days to weeks. The rash itself is usually not painful or itchy, which means people sometimes overlook it. If you’ve been in a tick-prone area and notice a slowly expanding circular red spot, that’s a strong signal to get evaluated promptly.
Pityriasis Rosea
This condition starts with a single large spot called a herald patch, typically 3 centimeters or more across, with a raised scaly border and a lighter, slightly depressed center. It may be the only spot for about two weeks. Then a secondary rash of smaller oval spots erupts across the trunk, upper arms, and upper thighs. On the back, these spots often follow the natural skin lines in a pattern that resembles a Christmas tree. On the upper chest, they tend to form a V shape. Pityriasis rosea is harmless and resolves on its own, usually within 6 to 8 weeks, but it can be alarming because it looks dramatic.
Bleeding Under the Skin: Petechiae and Purpura
Not all red spots are caused by inflammation or irritation. Some are caused by blood leaking from tiny broken vessels beneath the skin’s surface. These spots, called petechiae, are typically less than 3 millimeters across and look like small red, purple, or brown dots. Larger patches caused by bleeding from slightly bigger vessels are called ecchymoses, which resemble bruises. When petechiae spread and merge, they form purpura.
The critical distinction is whether the spots blanch. Blanching means the redness temporarily fades when you press on it. You can test this at home by pressing a clear glass against the spot. If the color disappears under pressure, blood is still flowing normally through the vessels, and the redness is from inflammation. If the spot stays visible through the glass and doesn’t fade at all, blood has leaked out of the vessels and is trapped under the skin.
When Red Spots Signal an Emergency
A non-blanching rash is the red flag that matters most. It can be a sign of meningococcemia, a life-threatening bloodstream infection that can become fatal within hours if untreated. The spots start small, often appearing first in areas where there’s pressure on the skin: the armpits, waistline, belt line, ankles, elbows, and inner thighs near the groin. Within hours, they can grow into larger, bruise-like patches that spread across the body.
The illness comes on fast and feels severe. People describe it as the worst they’ve ever felt. Other symptoms include high fever, violent chills or shaking, cold hands and feet, muscle pain, abdominal pain, extreme fatigue, and pale or discolored skin. If you or your child develops a spreading non-blanching rash with any of these symptoms, go to the nearest emergency room immediately. In the early stages of meningitis, the rash may still blanch, so a blanching rash combined with these severe symptoms also warrants urgent evaluation.
How to Narrow Down the Cause
A few questions can help you sort through the possibilities before you see a healthcare provider:
- Do the spots blanch? Press a clear glass against them. Non-blanching spots need urgent attention.
- Are you feeling sick overall? Fever, body aches, and fatigue point toward an infection.
- Are the spots itchy? Itching suggests hives, eczema, or an allergic reaction rather than bleeding under the skin.
- Where are they? A butterfly pattern on the face suggests lupus. Palms and soles suggest hand, foot and mouth disease. An expanding circle suggests Lyme disease.
- How fast did they appear? Hives come and go within hours. Viral rashes develop over a day or two alongside illness. Eczema and psoriasis build gradually over weeks.
- Did anything new happen recently? A new medication, food, insect bite, or illness in the days before the spots appeared can point toward the trigger.