Psoriasis is an inflammatory skin condition that creates red, scaly patches on the skin known as lesions or plaques. There are several causes of psoriasis, including stress, skin injuries, and medication. Bacterial infections, particularly strep throat, have also been found to cause certain types of psoriasis and trigger flare-ups in others.

Causes of Psoriasis

Psoriasis is an autoimmune condition. That means the body’s immune system attacks healthy tissues like it attacks invading pathogens (germs). In psoriasis, special immune cells known as T cells attack a person’s skin, causing inflammation. In turn, their body makes new skin cells much faster than normal, which leads to the formation of lesions.

Certain triggers and risk factors can contribute to the development of psoriasis. For example, genetics play a large role in determining who develops the disease. People with certain variations of human leukocyte antigen (HLA) genes, which affect the immune system, are more likely to have psoriasis. If you have a family history of psoriasis, you are at a greater risk of developing the condition yourself.

Environmental factors can also trigger psoriasis. Smoking, obesity, and bacterial infections are all linked to a higher risk of developing the condition.

How Strep Throat and Psoriasis Are Linked

Several studies have found that psoriasis is linked to bacterial infections. Specifically, psoriasis can be triggered by infections of group A streptococcus and group C streptococcus. These two strains of bacteria are behind the majority of strep throat infections.

The immune system’s main function is to recognize and destroy bacteria and viruses that enter the body. However, the system is not always perfect, and can sometimes cause damage to the body. Researchers believe that streptococci bacteria and skin tissue have one or some of the same “ingredients” in common. (In this case, it’s thought to be a shared protein — or antigen.)

To fight streptococci bacteria, a person’s immune system sends out T cells. These fighters identify a pathogen by its combination of surface proteins (or antigens). Once launched, T cells read the streptococci bacteria’s particular mix of antigens as an enemy, and attack. In someone with psoriasis, those strep-battling T cells could see which antigens the bacteria and healthy skin have in common, and attack the skin, too. Such an immune response would trigger inflammation in the skin and potentially lead to the development of psoriasis.

The Tonsils and Psoriasis

The tonsils — pads of flesh at the back of the throat — trap and collect germs that have entered the body through the mouth and nose. The tonsils are part of the lymphatic system (like the lymph nodes), and they store immune cells and help clear infections. Tonsils can become infected when a person has strep throat. (When that happens, they are said to have tonsillitis.)

In a person with psoriasis, their tonsils may become infected several times, and that can lead to flare-ups. Studies of the tonsils in people with psoriasis have found that their tonsils become infected more easily than those of people without psoriasis. That means in addition to dealing with a sore throat, a person with psoriasis also has to deal with their lesions worsening.

In many cases, the antibiotic penicillin can be given to fight the bacterial infection. However, for people who deal with recurrent infections, a tonsillectomy (removal of the tonsils) may be a better option. In fact, this procedure has been found to relieve symptoms in several forms of psoriasis, including plaque psoriasis, guttate psoriasis, and palmoplantar pustulosis.

Types of Psoriasis Related to Strep Throat

Strep throat can trigger the development of (or cause flare-ups in) certain types of psoriasis, including acute guttate psoriasis and chronic plaque psoriasis. These infections can also trigger a closely related condition known as palmoplantar pustulosis.

Acute Guttate Psoriasis

Guttate psoriasis is a specific type of psoriasis that develops suddenly. Its name stems from the Latin word for “drop” — gutta. With guttate psoriasis, scaly, red, teardrop-shaped spots form on a person’s arms and legs.

Around 8 percent of people who have psoriasis will develop guttate psoriasis at some point. For most people, this type of psoriasis occurs when they are children or young adults (under the age of 30), but it can appear at any age. The most common cause of guttate psoriasis is an infection — more specifically, strep throat.

Other causes of guttate psoriasis include:

• Other types of bacterial or viral infections (like upper respiratory infections)
• Skin injuries (burns, cuts, bug bites, and more)
• Stress
• Some medications (like antimalarials or certain drugs that treat heart conditions)

Chronic Plaque Psoriasis

Streptococcal infections have also been found to cause flare-ups in people with chronic plaque psoriasis. In fact, strep throat infections are 10 times as common in people with plaque psoriasis than those without. This increased prevalence is mostly likely because the immune system in people with psoriasis is dysregulated. The dysregulation makes it difficult for them to fight off infections.

Another Skin Condition Related to Throat Infections

Palmoplantar pustulosis (PPP) is a rare inflammatory disease in which liquid-filled blisters (pustules) develop on the soles of a person’s feet or palms of their hands. The condition is very similar to plaque psoriasis and psoriatic arthritis. In fact, some people have both PPP and plaque psoriasis together. As for its cause, PPP stems from bacterial infections like strep throat and tonsillitis.

Talk With Others Who Understand

On MyPsoriasisTeam, the social network for people with psoriasis and their loved ones, more than 104,000 members come together to ask questions, give advice, and share their stories with others who understand life with psoriasis.

Are you or a loved one living with psoriasis? Share your experience in the comments below, or start a conversation by posting on MyPsoriasisTeam.