Introduction 

Tattooing is the transfer of designs into the skin using ink with a needle. These permanent designs can vary in detail and size and can be applied almost anywhere on the body, although some areas are more suitable. Tattoos on your hands, feet, and face might twist or fade as skin gets older. Tattoos have held different meanings worldwide, dating back to the Ancient Egyptians. In some cultures, it signified social rank or identity towards a certain group. Individuals with tattoos were seen as rebellious and were associated with criminal activity. However, they have become popular forms of self-expression and artistic appreciation in recent decades. Due to the invasive process of tattooing, there are several risks of infection. These risks come from the body’s immune response. The inflammatory response is triggered by ink penetration in the skin. In this article, we discuss how tattoos alter the immune response.  It is important to understand these potential infections to ensure that appropriate aftercare follows.¹ 

Causes of tattoo infections

Tattoos can cause a range of infections in the body due to their impact on the immune system. The type of pathogen (disease-causing microbe) determines the type of infection. A common cause is inadequate aftercare. Wash and keep the tattoo soft often. The area should be protected from the sun, swimming pools and scab picking. Not following these instructions opens multiple gateways to infection. 

Bacterial infections

Bacterial infections can be found at different depths of the body. Superficial infections, such as impetigo, affect the outer layer of the skin. Cellulitis is a bacterial infection found in the deeper layers of the skin.² Cellulitis is caused by Streptococcus and Staphylococcus bacteria. This is the most common bacterium present after tattoo placements. When there is a break in the skin, these bacteria can enter the bloodstream and infect the body. In most cases, cellulitis itself is not serious, however, it can potentially lead to sepsis, which is life-threatening.³ Sepsis is known as a systemic infection. A bad shock can make all organs fail. 

During tattooing, the skin becomes ruptured due to repeated needle penetration, making it vulnerable to infection. Dirty tools and tattoo ink could lead to bad skin bugs. When tattoo artists mix different ink colours, some colours may be reused. Studies have shown that bacteria can accumulate in exposed ink bottles and utensils.² Precautions must be taken due to the high risk of bacterial contamination. 

Fungal infections 

Fungal infections arise similarly to bacterial infections. Exposure to specific fungi leads to the following infections: 

• Dermatophytes cause tinea.Tinea is a skin, nail, and hair infection that can spread by touching sick people or pets⁴
• Invasive mould disease (IMD) is a rare yet serious infection affecting the organs and blood vessels. It can enter the body through contaminated equipment or direct contact with the tattooed areas. There are two main types of IMD:
  • Aspergillosis is the most common and can spread from the skin to major organs.
  • Mucormycosis is a common form and has similar effects⁵
• Yeast infections may come from microorganisms contaminating the tattoo ink. This infection leads to an overgrowth of yeast on the skin or mucous membranes⁶

Viral infections

While tattoo-related infections are mostly bacterial, there have been reports of viral infections. For these cases, it was found that the infection remained local to the tattooed area. The viruses responsible are:

• Molluscum contagiosum virus (MCV) mimics the cytoplasm of cells and is found in the outer layer of the skin. It does not spread outside the tattooed skin and is most common when using black ink
• Human papillomavirus (HPV) is a DNA virus which infects the skin and mucous membranes. It makes skin bumps, only where the tattoo is. It was found that HPV was 7x more likely to form on black ink than coloured
• The herpes virus (HSV) has DNA and makes more of itself fast. HSV-1 is most common in tattoo infections and produces oral ulcers. It is mainly spread through skin-to-skin contact, saliva, instruments and ink⁷

Studies showed that these viruses were unlikely to survive in ink. Rather, the act of tattooing releases the viruses that are already present in the body. For example, HPV can lie dormant in the hair follicles. When that area of the skin is ruptured by the ink and needle, the virus is released into the body. 

Allergic reactions

Some people may be hypersensitive to tattoo ink and the aggressive application process. There are two main responses to tattoo ink:

• Allergic contact dermatitis
• Photoallergic dermatitis

There is little regulation on the composition of inks used, which means various chemicals can be used to achieve desired colours. The most common cause of the red, hot skin is the red ink in the tattoo, which has:

• Mercury sulfide 
• Ferric hydrate 
• Sandalwood 
• Brazilwood 
• Iron oxide 

Other pigments, such as black, blue, green and purple, are not associated with the hypersensitive response.⁸

Symptoms of tattoo infections 

The body suffers from many symptoms during a tattoo infection. This includes: 

• Rash or redness 
• Bumps in the tattoo area 
• Fever 
• Swelling 
• Puss 
• Increased pain 
• Chills 
• Sweats 
• Ulcers⁹

Immune system response to tattoo infections 

When you get a tattoo, your body sees the ink as foreign. The immune response is triggered, sending macrophages to destroy the invader. They do so by engulfing the ink and breaking it down through enzymes. However, the macrophages cannot break down large ink droplets. Instead, the molecules remain within the macrophage, this is the tattoo that we can see on the skin. After a few days, these macrophages die, and the ink molecule is released. The engulfing process is then repeated, keeping the tattoo in place. However, the smaller droplets are disposed of through the lymphatic system, leading to the tattoo fading over time.¹

In cases of infection, bacteria can enter the body through application. The tattoo gets infected with germs that grow fast. They grow faster than the white blood cells can fight them off. If several inflammatory responses fail to remove the bacteria, two types of infection may arise: chronic or acute. Acute infections are short-term and sudden. Usually, they are resolved within a few days or weeks. Chronic infections are long-lasting. The infection can persist for months or years due to the inability to fully clear the pathogen. People with lower immunity are at a higher risk of acquiring infections. This could be due to existing health conditions. 

Factors that weaken the immune response

The black ink can alter the immune response in the local cells. Research has shown that the black dyes can cause a local immunosuppressive effect. This means the local immune response is weakened, consequently, the ability to fight infections is weakened. Additionally, the broken down pigment in the macrophages impacts the lymph nodes and thus hinders the immune response. The polycyclic aromatic hydrocarbons in black ink are harmful to cells. These compounds can affect the membrane lipids and proteins, leading to the breakdown of the skin barrier. ⁷

Furthermore, tattoos exposed to excessive UV were followed by viral infections. This suggests that the virus remained in the skin until it was activated by UV exposure. The way the tattoo and sunburn change the skin's layers lets the virus spread. ⁷

Existing medical conditions, such as diabetes, HIV, and other autoimmune diseases, compromise the immune system. In diabetes, high blood sugar levels prevent white blood cells from effectively performing their functions. This can also trigger a chronic immune response, which prevents the body from recognising and responding to pathogens. As a result, the risk of skin infections increases. ¹⁰

Summary

Tattooing, while a popular form of self-expression, carries infection risks due to its invasive nature and the body’s immune response. Infections can arise from poor aftercare, contaminated tools, or ink. Common types include:

• Bacterial infections like cellulitis, often caused by Streptococcus or Staphylococcus, can lead to serious conditions like sepsis
• Fungal infections from dermatophytes, moulds, or yeasts enter through compromised skin.
• Viral infections such as HPV, HSV, and MCV, which often reactivate from dormant states due to skin trauma during tattooing
• Allergic reactions (e.g., dermatitis) are commonly linked to red ink, which contains harmful substances like mercury sulfide

The immune system responds by sending macrophages to engulf ink particles, but some particles remain, creating the tattoo. Infections occur when pathogens outpace the immune defences, especially in individuals with weakened immunity due to conditions like diabetes or HIV. Black ink and UV exposure can also suppress local immune responses, increasing infection risks. Proper aftercare and hygienic tattoo practices are critical for infection prevention.