What is an Mpox (Monkeypox) Lesion Test and How is the Fluid Sample Collected?

Noticing an unusual skin lesion or rash can understandably cause concern, particularly if you are aware of Mpox (formerly known as Monkeypox) and its reported symptoms. It is important to know that skin lesions and rashes can have several possible causes, many of which are entirely unrelated to Mpox or any sexually transmitted infection. Understanding what an Mpox lesion test involves — and when testing may be appropriate — can help reduce anxiety and support informed decisions.

Our clinic provides confidential STI testing services. We do not provide GP services or dermatology consultations, but we can advise on appropriate next steps if further medical care is needed.

Quick Answer: What is an Mpox Lesion Test?

An Mpox lesion test (also referred to as a Monkeypox PCR swab test) involves collecting a fluid or cellular sample directly from a skin lesion or blister. The sample is analysed in a laboratory to detect the presence of the Mpox virus. Appearance alone cannot confirm Mpox infection — laboratory testing is required for an accurate result.

Key points to be aware of:

• Skin lesions can have several possible causes
• Many rashes and blisters are caused by non-infectious skin conditions
• Appearance alone cannot confirm whether Mpox or another infection is present
• Testing may help clarify the cause when there is known exposure or persistent symptoms
• Mild cases may resolve without complications, but medical assessment is advisable

Symptoms alone cannot confirm an Mpox infection.

When Could Skin Lesions Be Linked to Mpox or an STI?

Skin lesions in or around the genital, anal, or oral areas — particularly following close physical or sexual contact with someone who has a confirmed or suspected Mpox diagnosis — may warrant consideration of an Mpox lesion test. However, lesions in these areas are also associated with other conditions including herpes, syphilis, and various non-infectious skin conditions. Testing is the only reliable way to identify the cause.

Section 1: Understanding Mpox and Its Symptoms

Mpox is a viral infection caused by the Monkeypox virus. It can present with a range of symptoms, typically beginning with flu-like signs such as fever, fatigue, swollen lymph nodes, and muscle aches. A distinctive rash or cluster of lesions often follows, which may appear anywhere on the body — including the face, hands, chest, genitals, and anal area.

The lesions typically progress through several stages: flat spots, raised bumps, fluid-filled blisters, pustules, and finally scabs. This progression can span one to four weeks. Not everyone experiences every stage, and in some cases, lesions may be limited in number or confined to a specific area of the body.

It is worth noting that many other conditions can produce similar-looking lesions, which is why visual assessment alone is not sufficient to confirm a diagnosis.

Section 2: Common Non-Mpox Causes of Skin Lesions

Skin lesions, blisters, and rashes in the genital or general body area are not exclusive to Mpox. Possible non-infectious causes may include:

• Contact dermatitis from soaps, lubricants, or latex
• Folliculitis (infected or inflamed hair follicles)
• Molluscum contagiosum (a common viral skin condition)
• Eczema or psoriasis flare-ups
• Ingrown hairs following shaving or waxing
• Blocked sebaceous glands
• Allergic reactions to clothing or products

These conditions can closely resemble early Mpox lesions in appearance, reinforcing why professional testing is important when there is genuine concern or a known exposure risk.

Section 3: Situations in Which Skin Lesions May Appear

Skin changes and lesions may occur in a variety of everyday circumstances unrelated to infection:

• After shaving or waxing: Irritation, ingrown hairs, and folliculitis are common
• After exercise: Sweat and friction can lead to skin irritation and minor rashes
• After sexual activity: Friction or sensitivity reactions may cause temporary redness or small bumps
• During hormonal changes: Shifts in hormone levels can affect skin condition and cause flare-ups
• After new skincare or hygiene product use: Reactions to unfamiliar ingredients are not uncommon

In many cases, such symptoms resolve on their own. If they persist or are accompanied by other symptoms, further assessment may be warranted.

Section 4: STIs That May Cause Similar Symptoms

Several sexually transmitted infections can produce lesions or skin changes that may, in some cases, look similar to Mpox lesions. These include:

• Herpes simplex virus (HSV): Can cause fluid-filled blisters around the genitals or mouth
• Syphilis: May cause painless sores (chancres) in the early stage, and a distinctive rash in the secondary stage
• HPV (Human Papillomavirus): Can present as warts or unusual skin growths
• Molluscum contagiosum: Small, dome-shaped lesions sometimes spread through sexual contact

Symptoms vary considerably between individuals. Many infections can also cause mild or no symptoms at all, making testing an important tool when exposure has occurred. If you are concerned about any of these infections, a full STI screen may provide helpful clarity.

Section 5: Why Symptoms Alone Cannot Confirm Infection

Many skin conditions share overlapping features — similar size, shape, colour, or distribution. A healthcare professional cannot visually diagnose Mpox or most STIs with certainty, and neither can an individual assessing their own symptoms. Laboratory analysis of a sample is required to confirm or rule out specific infections. This is true for Mpox, herpes, syphilis, and numerous other conditions.

Section 6: When Mpox or STI Testing May Be Sensible

Testing may be worth considering if any of the following apply:

• You have had close physical or sexual contact with someone with a confirmed or suspected Mpox diagnosis
• You have developed unexplained lesions, blisters, or a rash — especially accompanied by fever or swollen glands
• Symptoms are persisting beyond a few days without an obvious cause
• You have had a new sexual partner or unprotected sex and are experiencing unusual symptoms
• A sexual partner has been diagnosed with an STI

Section 7: How an Mpox Lesion Test Works

An Mpox lesion test typically involves the following steps:

Sample Collection

A healthcare professional uses a sterile swab to collect fluid or cellular material directly from an active lesion. The roof of a blister may be gently broken to access the fluid within. In some cases, a dry swab of the lesion surface may be sufficient.

Laboratory Analysis

The collected sample is sent to a laboratory, where a PCR (polymerase chain reaction) test is performed. PCR testing detects the genetic material of the Mpox virus with a high degree of accuracy.

Results

Results are typically returned within a few days, depending on the testing provider and laboratory. Confidential results processes vary between clinics.

It is important that the swab is taken while lesions are active. Testing from healed or crusted lesions is generally less reliable.

Section 8: When Symptoms Are Less Likely to Be Mpox

In many cases, skin changes are the result of temporary, benign causes. The following scenarios are generally considered lower concern:

• A single small bump following shaving that resolves within a few days
• Mild redness after friction during exercise or sexual activity
• A localised rash in response to a new product or detergent
• Minor skin changes without any accompanying systemic symptoms (such as fever or fatigue)

If symptoms are isolated, short-lived, and have a clear apparent cause, they may not require Mpox testing. However, if there is any genuine uncertainty — especially following potential exposure — seeking appropriate assessment is always a reasonable step.

Section 9: Frequently Asked Questions

Can a rash or lesion always indicate Mpox?

No. Rashes and lesions have many possible causes, including non-infectious skin conditions, allergies, and other infections. Testing is necessary to confirm any specific cause.

Should I get tested if my symptoms have already disappeared?

If symptoms have resolved and there was no known exposure, testing may not be necessary. However, if you had a recent potential exposure, it may still be worth discussing testing with an appropriate service, as some infections can be present without visible symptoms.

How soon after potential exposure should testing be done?

For Mpox, testing is most reliable when active lesions are present. If you believe you have been exposed, contact an appropriate healthcare service as promptly as possible for guidance.

Is the lesion swab procedure painful?

Mild discomfort may be experienced during swabbing of an active lesion, particularly if the area is tender. The procedure is brief and carried out with care.

Can Mpox be spread through sexual contact?

Mpox can be spread through close physical contact, including sexual contact. It is not classified solely as a sexually transmitted infection — transmission can also occur through other forms of skin-to-skin contact, respiratory droplets, or contact with contaminated materials.

Does a negative lesion test rule out all STIs?

No. An Mpox lesion test specifically screens for the Mpox virus. Separate tests are required for other STIs such as chlamydia or gonorrhoea. A full STI screen may be advisable if broader concerns exist.

Section 10: When to Seek Medical Advice

Certain symptoms may indicate a need for prompt medical assessment beyond standard STI testing. These include:

• Rapidly spreading rash or a high number of lesions across the body
• Severe pain associated with lesions
• Fever, fatigue, or swollen lymph nodes alongside a rash
• Lesions near the eyes or mouth
• Symptoms that are worsening rather than improving
• Lesions in immunocompromised individuals

If symptoms persist or worsen, consultation with an appropriate healthcare service — such as a sexual health clinic, NHS 111, or your GP — is advised.

Confidential STI Testing in the UK

If you are concerned about possible Mpox-related symptoms, recent exposure, or broader STI risk, confidential STI testing appointments are available at our UK clinic. Testing decisions depend on symptoms, exposure history, and individual risk factors. Our team can advise on which tests may be appropriate for your circumstances.

Visit sticlinic.co.uk to find out more about available testing services.

This article is for general informational purposes only and does not constitute medical advice, diagnosis, or treatment. Sexual health concerns should be assessed based on individual circumstances. If you are experiencing persistent, severe, or worsening symptoms, consultation with an appropriate healthcare service is advised. Our clinic provides private STI testing services only.