Cold sores, also known as fever blisters, are common viral infections around the mouth. They are caused by the herpes simplex virus (HSV), most often HSV-1. This article helps identify cold sores, their progression, and how to distinguish them from other conditions.
Key Visual Signs and Early Symptoms
Cold sores often begin with distinct sensations before any visible signs. Many report tingling, itching, burning, or numbness around the lips a day or two before a sore appears. This initial phase, called the prodromal stage, signals the sore’s emergence. The area may also become red and swollen.
After these sensations, small, red bumps or blisters emerge. These painful, fluid-filled blisters often appear clustered along the lip border. Multiple small, clustered blisters are a characteristic feature. While most often seen around the mouth, cold sores can also appear near the nose, on the chin, or on the cheeks.
How Cold Sores Evolve
Cold sores progress through several distinct stages. Small bumps quickly develop into fluid-filled blisters, which are often grouped. These blisters contain clear or slightly yellow fluid and are highly contagious during this phase. Within a few days, typically around days two to three, these blisters rupture.
The blisters burst, leading to shallow, open sores that may ooze fluid, known as the “weeping stage.” A yellowish or brownish crust (scab) then forms over the open sores. This crusting indicates healing, though the scab may crack and bleed if stretched. The scab eventually dries, shrinks, and flakes off, with the underlying skin healing, often without a scar. Cold sore outbreaks typically resolve within 7 to 10 days, though some can last up to two weeks or more, especially during a first outbreak.
Telling Cold Sores Apart from Other Conditions
Distinguishing cold sores from other common mouth conditions is important. Canker sores (aphthous ulcers) are often confused with cold sores, but differ in location and cause. Canker sores develop exclusively inside the mouth, on soft tissues like the tongue, gums, or inner cheeks, and are not caused by the herpes simplex virus. In contrast, cold sores appear on or around the lips and are viral.
Pimples or acne can also appear near the lips. Cold sores present as a cluster of tiny blisters, often with a tingling or burning sensation before visibility. Pimples usually appear as a single raised red bump, may develop a whitehead, and lack prodromal tingling. Pimples are caused by clogged hair follicles.
Allergic reactions or chapped lips can also cause lip irritation. Chapped lips involve widespread dryness, cracking, and tenderness across the lip surface, without localized blister formation. Allergic reactions on the lips, like contact dermatitis, often present as generalized swelling, redness, or a rash across a broader area, not specific fluid-filled blisters. Eczema on the lips also appears as dry, scaly, and itchy skin. While it can involve blisters, initial symptoms usually develop all at once, differing from a cold sore’s tingling onset.