Psoriasis Triggers: What Causes Flare-Ups and How to Avoid Them

Your skin had been calm for weeks, and then, seemingly out of nowhere, the red, scaly patches are back. If you live with psoriasis, you know that flares can feel random and frustrating. But they usually aren't random at all. Most flares are set off by a trigger, and once you learn yours, you gain real control over how often your skin acts up.

Psoriasis is a long-term condition rooted in your genes and immune system, but it tends to flare in response to specific triggers like stress, infection, skin injury, cold weather, and certain medications. The catch is that triggers vary from person to person, so part of managing psoriasis is detective work. Here is what the most common triggers are and what you can do about them.

What is a psoriasis trigger?

A trigger is anything that sets off a new psoriasis flare or makes existing patches worse. Psoriasis itself is not caused by triggers. According to the American Academy of Dermatology (AAD), the condition comes from a genetic predisposition combined with immune dysfunction, where your immune system speeds up the life cycle of skin cells. Triggers are the events that push that overactive system into a visible flare.

This distinction matters. You cannot give yourself psoriasis by being stressed or getting a sore throat, but if you already carry the genetic and immune setup, those things can light the fuse. Psoriasis is common, affecting roughly 2% of people worldwide and up to about 4% in the United States and Canada, so a large number of people are managing these same triggers.

The most common psoriasis triggers

The AAD and Mayo Clinic point to a familiar short list of culprits. Triggers vary from person to person, but most flares trace back to one of these:

• Stress, both emotional (a major life event like job loss or bereavement) and physical (illness, fatigue, or sleep deprivation). Stress is one of the most commonly reported triggers.
• Infections, especially strep throat, which is strongly linked to a form called guttate psoriasis.
• Skin injury, including cuts, scratches, bug bites, tattoos, and sunburn (this is called the Koebner phenomenon).
• Cold, dry weather, which pulls moisture from the skin.
• Certain medications, including lithium, beta-blockers, and antimalarial drugs.
• Lifestyle factors such as smoking, alcohol use, and obesity, which are established risk factors and can worsen flares.

How infection and strep throat trigger flares

One of the best-documented triggers is streptococcal infection. A strep throat (caused by Streptococcus pyogenes) can set off guttate psoriasis, a type that shows up as small, drop-shaped spots scattered across the trunk and limbs.

The timing is fairly predictable. Peer-reviewed research has shown that guttate lesions classically follow a preceding strep infection, with the spots typically appearing 1 to 3 weeks after the sore throat. If you or your child develops a sudden shower of small psoriasis spots after a recent sore throat, mention the connection to your clinician, since treating the underlying infection is part of the picture.

How skin injury and weather trigger flares

The Koebner phenomenon is one of the more surprising triggers. It means new psoriasis lesions can form at the exact spot where your skin was injured, including from scratching, cuts, irritation, or sunburn. This is why protecting your skin from trauma, and resisting the urge to scratch, is a practical part of flare prevention.

Weather plays a role too. Cold, dry air, common in winter, strips moisture from the skin and is a frequent trigger. Sunburn works in the opposite direction as a form of skin injury that can provoke the Koebner response. The goal is balance: keep skin well moisturized in cold months and protected from burning in the sun.

Which medications can trigger psoriasis?

Some prescription drugs are well-known to worsen or trigger psoriasis, a pattern sometimes called drug-induced psoriasis. According to DermNet, the most documented offenders are lithium, which worsens or triggers psoriasis in roughly 50% of patients who have the condition, and beta-blockers, which affect about 20%. Antimalarial drugs such as hydroxychloroquine and chloroquine are also recognized triggers.

This does not mean you should stop a prescribed medication on your own. These drugs are often important for treating other conditions. Instead, tell the prescribing clinician about your psoriasis so they can weigh alternatives or monitor your skin. Never adjust or discontinue a medication without medical guidance.

How to find and manage your own triggers

Because triggers are so individual, the most useful tool is awareness. The AAD notes that identifying and managing your personal triggers leads to fewer flares. A simple flare diary, where you jot down what was happening in the days before a flare (a cold, a stressful week, a new medication, a sunburn), can reveal your patterns over time.

From there, the strategies are practical: manage stress, treat infections promptly, moisturize in cold weather, protect your skin from injury and sunburn, and address lifestyle factors like smoking and alcohol. If your flares are frequent, severe, or not responding to over-the-counter care, a clinician can help you build a personalized plan and consider prescription treatment.