Psoriasis flares are driven by a mix of immune triggers, from stress and infections to medications, weather changes, and lifestyle habits. Around 60 million people worldwide live with psoriasis, and for most of them, symptoms come and go in cycles. A typical flare lasts anywhere from a couple of weeks to a few months. Understanding what sets one off is the most practical step you can take toward keeping your skin calm for longer stretches.
Stress and the Immune Feedback Loop
Stress is one of the most commonly reported psoriasis triggers, and the biology behind it is more involved than simple “stress makes things worse.” When you’re under psychological stress, your brain ramps up production of a hormone called CRH, which kicks off a chain reaction through your adrenal glands, ultimately releasing cortisol. Cortisol is your body’s natural anti-inflammatory compound. That sounds helpful, but here’s the problem: chronic stress floods your system with so much cortisol that your cells stop responding to it properly. The receptors that normally receive cortisol’s calming signal become desensitized.
The result is a paradox. Patients with psoriasis who report high stress levels actually have lower cortisol levels in their saliva, not higher. Their anti-inflammatory brake pedal stops working. Meanwhile, stress hormones like epinephrine trigger separate inflammatory pathways, boosting the same inflammatory molecules that drive psoriasis plaques. CRH also acts directly on skin cells, causing mast cells to release their contents, increasing blood vessel permeability, and promoting the growth of new blood vessels, all hallmarks of a psoriasis flare.
Infections, Especially Strep Throat
Streptococcal throat infections are a well-established trigger for psoriasis, particularly the guttate form that shows up as small, widespread, drop-shaped spots rather than thick plaques. This connection is strongest in children and young adults. The link is immunological: strep bacteria activate a specific branch of the immune system involving IgA antibodies and a type of inflammatory cell that produces IL-17, one of the key drivers of psoriasis. Patients with psoriasis show a heightened IgA response to strep bacteria compared to people without the condition, which helps explain why a routine sore throat can cascade into a full skin flare.
Guttate flares triggered by strep often appear one to three weeks after the infection. For some people, these are isolated episodes that clear up. For others, strep-triggered guttate psoriasis is the first sign of a chronic condition that later transitions into plaque psoriasis.
Skin Injuries and the Koebner Phenomenon
About 25 to 30 percent of people with psoriasis experience what’s called the Koebner phenomenon: new plaques forming exactly where the skin has been injured. Cuts, burns, sunburns, bruises, insect bites, and even animal stings can all set it off. The injury doesn’t have to be dramatic. Chronic friction from a waistband, belt buckle, or bra strap is enough to trigger new lesions in those areas.
This is worth keeping in mind during everyday life. Tattoos, surgical incisions, and even aggressive scratching of itchy skin can provoke new plaques at the injury site. If you know you’re prone to this response, protecting your skin from unnecessary trauma, including sunburn, becomes a practical way to prevent flares in new locations.
Medications That Trigger or Worsen Flares
Several common medication classes can provoke psoriasis flares, sometimes severely. The drugs with the strongest evidence include:
- Beta-blockers (prescribed for high blood pressure and heart conditions): These are considered a major factor in triggering or worsening psoriasis. Even timolol eye drops used for glaucoma have been reported to cause flares, since the medication passes into the bloodstream through the eye’s surface.
- Lithium (used for bipolar disorder): Skin reactions occur in roughly 3 to 45 percent of patients on lithium, making it one of the more common culprits. It can trigger new psoriasis in people with no personal or family history of the disease.
- Antimalarial drugs: Chloroquine and related medications worsen psoriasis in a significant number of patients. In one study of American soldiers with psoriasis given chloroquine for malaria prevention, 42 percent experienced flares that were resistant to treatment.
- NSAIDs (ibuprofen, naproxen, and similar pain relievers): These over-the-counter drugs can aggravate existing psoriasis in some people.
- Tetracycline antibiotics: Another class with a recognized link to psoriasis provocation.
If you notice your psoriasis worsening after starting a new medication, that connection is worth flagging. Stopping a medication abruptly isn’t safe without guidance, but knowing the link helps you and your prescriber weigh alternatives.
Cold Weather and Low Humidity
Seasonal changes affect roughly 60 percent of people with psoriasis, and the pattern is consistent: symptoms worsen in cold, dry months and improve in warmer, more humid seasons. This isn’t just about comfort. Cold temperatures reduce the skin’s natural oil production, weaken the outer barrier layer, and disrupt the balance of microbes living on the skin’s surface. Low humidity compounds the problem by pulling moisture out of the skin, degrading the structural proteins that hold the barrier together, and increasing water loss through the surface.
The practical takeaway is that winter demands more aggressive moisturizing. Keeping indoor humidity above very dry levels and applying thick emollients right after bathing can help offset what the season is doing to your skin barrier.
Smoking and Alcohol
Smoking nearly doubles the risk of developing psoriasis, and it worsens outcomes for people who already have it. One large analysis found a 70 percent higher psoriasis risk among smokers. The effect is dose-dependent, meaning heavier smoking correlates with more severe disease.
Alcohol contributes through multiple routes. It impairs liver function (which affects how the body clears inflammatory byproducts), disrupts gut barrier integrity, and can interfere with psoriasis medications. Heavy drinking is also associated with poor treatment adherence, creating a cycle where flares become harder to control. Reducing or eliminating both habits is one of the few lifestyle changes with strong evidence behind it for psoriasis management.
Obesity and Chronic Inflammation
Excess body fat isn’t just stored energy. Fat tissue functions as an immune organ, producing its own inflammatory molecules, including several of the same ones that drive psoriasis. When someone becomes obese, immune cells called macrophages accumulate in fat tissue, and the secretion of inflammatory compounds ramps up significantly. These include TNF-alpha, IL-6, and IL-17, all central players in psoriasis.
This creates a self-reinforcing cycle. Obesity raises your baseline level of inflammation, making flares more frequent and harder to treat. Weight loss has been shown to improve psoriasis severity independently of other treatments, which is why it’s considered a meaningful part of long-term management for people carrying significant extra weight.
Diet: What the Evidence Actually Shows
Dietary triggers get a lot of attention online, especially gluten and dairy elimination. The evidence, however, is limited. A few small, uncontrolled studies have shown improvement in psoriasis severity with a gluten-free diet, but the National Psoriasis Foundation recommends against going gluten-free unless you have confirmed gluten sensitivity or celiac disease. For most people with psoriasis, eliminating gluten won’t make a measurable difference.
That said, overall dietary pattern matters more than any single food. Diets high in processed foods and sugar promote systemic inflammation, while anti-inflammatory eating patterns (rich in vegetables, fish, and whole grains) may support lower baseline inflammation. The effect is modest compared to triggers like stress, infection, or medication, but over time, it adds up as part of a broader strategy.
How These Triggers Interact
Psoriasis flares rarely come from a single cause. More often, it’s a combination: a stressful month at work, cold dry weather pulling moisture from your skin, and a couple of nights of heavier drinking that together push your immune system past its threshold. This is why someone can handle one trigger without problems but flare when two or three overlap. Tracking your flares alongside potential triggers, even informally, can help you identify your personal pattern over time. Most people find that one or two triggers dominate their experience, and managing those specifically yields better results than trying to control everything at once.