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Herpes (Cold Sore) or a Pimple? How to tell the difference

In Basic Science, Infectious Diseases on September 17, 2011 at 9:57 pm

Herpes (Cold Sore) or a Pimple (acne)?  How to tell the difference


I could see the panic in his eyes. “What is it doc? Is it herpes?”  Running through his mind were worries of what to tell his wife. Where did I get it. Or did I get it from my wife? Has she been faithful? Is she going to think I have not been faithful. Is this going to be an ongoing problem the rest of my life?


In my opinion the fear attached to herpes is a little overblown, but it can be a real nuisance especially if it is genital herpes. In this article I will only discuss how to differentiate herpes from a common pimple. I have had a number of patients come to see me for this reassurance, so let me show you how to differentiate the two.

Let’s learn a medical term. (Do not panic, a big word is coming.)  Herpetiform.  Herpetiform is a medical descriptive term for a rash having the appearance of clusters of blisters. There are only a few rashes that appear as clusters of blisters. One is herpes simplex (cold sores). Shingles (herpes zoster) is another. Other “herpetiform” rashes are pretty rare. So the first step in evaluating a rash where herpes is the concern is to look for clusters of blisters. If it is on the lip, and is painful and is a single cluster (walks like a duck, quacks like a duck) you are most likely dealing with herpes simplex (cold sore). The reason I said it needs to be a single cluster is because shingles can look the same, but shingles will almost always have multiple clusters. (I will be writing an article about shingles in the future.) Another thing to look for is the location of the blisters. Usually with cold sores the clusters of blisters will be very near the border of the colored part of the lip and the skin of the face, called the vermillion border. The photo on the left is an excellent example of a typical cold sore. One possible confusing element though is that these blisters can easily break. The fluid contained is watery and clear. If the blisters break you will be left with a superficial erosion or ulcer like the picture on the right.


Pimples are plugged up oil glands that become infected. So usually, there is a small nodular area with a “white head” or pustule on top.  The picture on the left clearly shows the nodularity deeper in the skin, and the pustule on the surface. If you gently press the nodule the pustule will rupture and the fluid expressed will be thick and creamy colored. Any pain or tenderness is usually mild. With herpes the pain can be searing and intense, especially if it is the first outbreak.

I hope this helps you to tell the difference between pimples and cold sores.



 How To Tell If A Wound Is Infected

I often see patients with minor wounds who come in to be seen because of a concern over infection. This article will help you to recognize the signs and symptoms of infection.

Any break in the defense mechanism of the skin can allow infection in. It does not require an injury bad enough to bleed. Severe dryness of the skin, or a minor sunburn can be enough to allow infection. Once the defense mechanism of the skin is disrupted bacteria can enter, begin to multiply and cause infection.

Let me explain the response mounted by your defense mechanism and you will more readily recognize signs and symptoms of infection. The skin has mechanisms in place to quickly recognize infection. An army of fighters is called to the site of infection to begin the fight. Blood vessels in the area dilate to increase blood circulation in the area to allow the army of fighters to get there. The dilation of blood vessels causes the skin to appear red and feel warm. The dilated blood vessels become leaky to further allow the fighter army into the fight, and the leaky blood vessels cause swelling in the area.  Most of the fighter cells are white blood cells (this is the main component of pus). These cells release chemicals to intensify the process causing more redness and warmth and now pain and tenderness. This entire process is called “inflammation.”

The defense army will attempt to wall off the infection to prevent the infection from invading deeper and wider. If this effort is successful the infection becomes walled off and an abscess (like a big pimple) develops.  As the infection is being walled off the surface skin thins and looks like  a white head. The purpose of thinning the skin is to eventually open up and eject the infection out of the body.

If your defense mechanism fails to wall off the infection, the infection will continue to spread either deeper into the skin and underlying structures, or superficially in the plane of the skin. This superficial spreading infection is called “cellulitis.” If the infection invades deeper into the skin and underlying structures the wound will become more swollen, tender, red and warm. A white head will eventually develop. If the infection just spreads horizontally (this is cellulitis and is more usual for uncontrolled infection). What you will see is an enlarging circle of redness, warmth and tenderness spreading from the center of the wound. The area of redness can be fast, extending several inches in a day. Cellulitis will also cause the classic “red streak.” This is called “lymphangitis.”  This  is the infection spreading up the lymphatic system. The read streak will head in a direction up the arm or leg toward the heart, and will cause local lymph glands to swell. At some point fever, chills and sweats will develop.

Of note is that some of this will happen just as a result of injury.  A cut or scrape will cause some redness and warmth for similar reasons as infection. The skin recognizes the injury and dilates blood vessels to mobilize an army of cells to come to heal the injury and to prevent infection. This redness and warmth will be minor, confined to the area close to the wound, and it will not generally be tender. No pus will be seen, and there will be no fever.  The extent of the redness will be stable or decreasing, certainly not expanding two inches daily like cellulitis.


Signs and symptoms of infection developing in a wound

1. Pus: If you see thick discolored drainage coming from a wound, it is infected

2. An abscess: If the area around the wound keeps swelling more and more, and getting more tender, and developing a white head on top, this is probably an abscess.

3. Cellulitis: Cellulitis is a superficial spreading infection in the skin. Instead of having the normal small area of redness around a healing wound, the redness expands rapidly, often two or three inches daily. It is becoming more painful and tender and warmer.

4. A Fever over 100.5 °F, chills and sweats indicates infection.

5. Inflammation: The four elements of inflammation are redness, warmth, swelling, and tenderness. There will be slight inflammation around a wound. when infected the inflammation will get worse every day, while in a normal healing wound it will be stable, or lessening every day.


Disclaimer:The information presented here and in other articles on this website is meant for general information only, and not for specific treatment recommendations. Nothing contained or offered by, on or through should be construed as medical advice or relied upon for medical diagnosis or treatment. Speak with your physician or healthcare provider for more information on this topic. This is copyrighted material ©2011, all rights reserved


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