HIV Rash vs. Syphilis Rash: What Are the Differences?

HIV rash occurs when the body’s immune system reacts to an acute HIV (human immunodeficiency virus) infection, usually two to four weeks after exposure but can appear as early as a few days after exposure.

Syphilis rash is a symptom of secondary syphilis, meaning it appears if syphilis isn’t treated after the first symptoms appear. However, a rash may be the first symptom of syphilis a person notices. This is because the initial symptom (an often painless ulcer) can go unnoticed, especially if it's in a location that's harder to see.

Rash is a symptom of both HIV and syphilis, but how each rash looks and where it appears on the body—along with other HIV symptoms and syphilis symptoms—are characteristics that differentiate one infection from the other.

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This article discusses the differences between HIV rash and syphilis rash and provides some characteristic signs.

If you are concerned about a rash or a potential exposure to a sexually transmitted infection (STI), be sure to see a healthcare provider for a proper diagnosis so that you can get the appropriate treatment right away.

Symptoms

Both HIV rash and syphilis rash can look similar. They may be red and patchy, and HIV and syphilis have some overlapping symptoms, including swollen lymph nodes and flu-like symptoms (such as fever, chills, and muscle aches). But where these rashes show up on the body and specific characteristics can help differentiate them. 

HIV rash is a red patch with small bumps that usually appears on the upper parts of the body. It can be itchy and painful. Mouth ulcers may also develop along with a rash.

Syphilis rash is not itchy and often appears as red or red-brown spots that are often too light to even be seen. The rash can appear anywhere on the body, but it typically develops on the chest, back, or arms. Rashes can even appear on the soles of the feet or palms of the hand.

A syphilis rash may appear in another form—large raised wart-like gray or white spots on moist parts of the body, such as the groin or armpits.

Causes

The causes of HIV rash and syphilis rash are similar in that both HIV and syphilis are sexually transmitted infections (STIs). However, unlike syphilis, HIV can be transmitted through intravenous drug use.

Some data suggest a link between acquiring HIV and syphilis. For example, having another STI, such as syphilis, is a risk factor for acquiring HIV.

In the United States, about half of men who have sex with men (MSM) and who have primary syphilis or secondary syphilis also have HIV. In addition, MSM who have primary or secondary syphilis are more likely to get HIV.

Verywell Health prefers to use inclusive terminology. But when citing research or health authorities, the terms for gender or sex from those sources are used.

Causes of HIV Rash

HIV rash usually develops shortly after contracting HIV, but a rash can also occur in advanced stages of HIV or as a side effect of HIV medications.

Causes of Syphilis Rash

Syphilis rash marks the secondary stage of syphilis, which occurs if syphilis isn’t treated during the primary stage. The primary stage is marked by a chancre (a painless, firm, round lesion) which shows up on the genitals, anus, or mouth—wherever syphilis entered the body.

Syphilis rash can show up either when the chancre is still present and healing or weeks after the chancre has already healed.

Diagnosis

A healthcare provider will be able to diagnose an HIV rash and a syphilis rash. The healthcare provider may examine the rash and take a blood sample for an HIV test or syphilis test. Taking fluid from a sore that is suspected to be a syphilis sore is also a way to test for syphilis. Saliva and urine can also be tested for HIV.

Treatment

Successful treatment for HIV rash and syphilis rash depends on getting the right diagnosis. Always see a healthcare provider if you are concerned that you may have HIV or syphilis or the associated rashes so you can get the right treatment. Treating an HIV or syphilis rash also means treating the underlying infection.

HIV Rash Treatment

The first symptoms of HIV may go away within a couple of weeks. If an HIV rash is severe, a healthcare provider may prescribe hydrocortisone cream to help relieve itching and swelling. It's important to start HIV treatment with antiretroviral therapy right away to best manage the condition.

Syphilis Rash Treatment

A syphilis rash will go away even if you don’t get treatment, but syphilis treatment is needed as soon as possible to keep the infection from progressing.

Syphilis can be cured with the right antibiotic medication. Treatment for secondary syphilis, of which syphilis rash is a symptom, is the same as for primary syphilis and generally requires an intramuscular injection of penicillin.

Prevention

Having sex without a condom can make you vulnerable to both HIV and syphilis. Avoiding condomless sex is the best way to prevent HIV and syphilis. For people who inject drugs, using new, clean needles is crucial to preventing transmission.

People living with HIV will not typically transmit HIV sexually if they are undergoing antiretroviral therapy and have an undetectable HIV viral load. They may not need to use a condom to prevent transmission of HIV, but a condom would reduce the risk of transmitting or acquiring other STIs.

Getting tested for STIs and ensuring any sexual partner has been tested is another important step in prevention.

HIV Rash Prevention

Preventing HIV rash means knowing the risk factors for HIV. Key factors for prevention include but are not limited to:

• Condom use
• Prevention and testing for HIV and other STIs
• Antiretroviral drug use (such as pre-exposure prophylaxis, or PrEP)
• Safe drug use for people who inject drugs

Knowing your status and that of your partner is crucial to preventing HIV transmission. Getting tested and getting access to antiretroviral drugs, if appropriate, is key to keeping yourself free from HIV. Talk to a healthcare provider if you are concerned about HIV or have questions about how to protect yourself.

Syphilis Rash Prevention

Using a condom is important for preventing syphilis rash since contact with a partner's sores can transmit the infection to you. However, some sores may not be covered by a condom, and thus avoiding contact with those sores is key to preventing infection.

Syphilis rash is a symptom of secondary syphilis. Getting timely treatment at the first sign of syphilis is crucial to keeping syphilis from lingering and advancing to later stages and symptoms such as syphilis rash.

Regular testing for syphilis is important if you:

• Are a man who has sex with men
• Have HIV
• Are taking PrEP
• Have a partner who has syphilis

Talk to a healthcare provider if you are concerned you might be at risk for syphilis or have questions about prevention.

Summary

HIV rash and syphilis rash may have similarities in appearance, but there are distinguishing features and factors of each. Where the rash shows up on the body as well as additional signs and symptoms can help differentiate them.

For example, an HIV rash is usually itchy and seen on the upper part of the body, while a syphilis rash is not usually itchy and often shows up on the palms of the hands or soles of the feet.

Proper diagnosis of HIV rash and syphilis rash, and therefore HIV and syphilis, respectively, is key to getting the right treatment. Both HIV and syphilis rashes can be prevented by knowing and managing the risk factors for HIV and syphilis.