What Causes Psoriasis? Triggers, Genes and How to Manage Flares

If you have psoriasis, someone has probably asked what you did to get it. The honest answer is nothing. Psoriasis comes from a mix of genes you were born with and an immune system that overreacts, and something in everyday life usually lights the fuse: an infection, a stressful month, a cut or sunburn, a new medicine or a cold, dry winter.

The tendency is lifelong, but many triggers can be spotted and managed, which is why understanding them is one of the most useful things you can do. This guide walks through the three pieces, what tends to set off flares and what helps.

What happens in the skin

Healthy skin replaces itself slowly: new cells form in the bottom layer and take about a month to reach the surface and flake away. In psoriasis, immune cells called T cells become overactive in the skin. They release chemical messengers that cause inflammation and tell skin cells to multiply much faster, so new cells reach the surface in a matter of days.

The skin cannot shed them quickly enough, so they build up into thick, raised plaques with a silvery scale. Extra blood vessels form under the plaque, which is why it looks red on lighter skin, or purple, grey or dark brown on brown and Black skin.

Some of those messengers have names you may see on medicine leaflets, such as TNF, IL-17 and IL-23. Many of the most effective modern psoriasis medicines, called biologics, work by blocking one of them. That is good evidence that the immune system, not the skin itself, is the root of the problem.

Because the cause is inside the body, psoriasis cannot be passed from one person to another. We explain this in more detail in is psoriasis contagious?

Is psoriasis genetic?

Genes play a big part. Psoriasis often runs in families, and having a parent, brother or sister with it makes you more likely to develop it. Researchers have linked many genes to psoriasis; one of the strongest is a version of an immune gene called HLA-Cw6, which is common in people whose psoriasis starts before the age of 40.

But genes are not destiny. Many people who carry psoriasis genes never develop it, and some people with no family history do. In most cases, psoriasis appears when a person with the tendency meets the right trigger.

Common psoriasis triggers and what helps

Triggers vary from person to person. These are the ones most often linked to the first appearance of psoriasis or to flares:

Trigger	How it sets off psoriasis	What helps
Strep throat and other infections	Infections switch the immune system on. Strep throat is the classic trigger for guttate psoriasis, sudden small drop-shaped spots	Get a sore throat checked and treated promptly
Stress	One of the most common triggers. Flares often follow a stressful few weeks	Sleep, exercise and stress management; counseling if it is constant
Skin injury	New plaques can form in a cut, scratch, bug bite, sunburn or tattoo (the Koebner response)	Protect your skin, avoid picking and scratching, use sunscreen
Cold, dry weather	Less sunlight and humidity; many people flare in winter and improve in summer	Thick moisturizers, a humidifier, short lukewarm showers
Some medicines	Lithium, beta-blockers (blood pressure medicines), antimalarials such as hydroxychloroquine and some anti-inflammatory painkillers can worsen psoriasis	Tell your prescriber you have psoriasis. Never stop a prescribed medicine on your own
Stopping oral steroids suddenly	Coming off steroid tablets such as prednisone quickly can cause a severe rebound flare	Steroid tablets should be tapered under medical supervision
Smoking and alcohol	Both are linked with more psoriasis and more severe flares	Cutting down or quitting helps your skin and your treatment
Excess weight	Linked with more severe psoriasis and with treatments working less well	If you are overweight, losing weight often improves psoriasis

Some people also notice flares with particular foods or allergies. The evidence for any single food is weak, so we do not recommend strict elimination diets, but if you see a clear pattern it is worth noting.

What causes scalp psoriasis?

Scalp psoriasis has the same cause as psoriasis elsewhere: the immune system and your genes, set off by the same triggers. The scalp is simply one of the most common places for plaques to appear, along with the elbows, knees and lower back. Scratching, harsh hair products, tight hairstyles and hot hair tools can injure the scalp and keep plaques going.

It is often confused with dandruff (seborrheic dermatitis), which has softer, greasier, yellowish flakes; psoriasis plaques are usually thicker, more sharply defined and often extend past the hairline. A medicated shampoo can help either, but scalp psoriasis usually needs a prescription treatment to settle.

What does not cause psoriasis

• Catching it from someonePsoriasis is not contagious.
• Poor hygieneWashing more does not prevent it, and scrubbing plaques makes them worse.
• Something you did wrongIt comes from your genes and immune system, not from your choices.
• A single foodNo one food causes psoriasis, though overall diet and weight can affect it.

Psoriasis is more than skin deep

Because the immune system is involved throughout the body, psoriasis is linked with other health conditions. People with psoriasis have a higher risk of psoriatic arthritis, and of diabetes, high blood pressure and heart disease. If you have joint pain, morning stiffness, swollen fingers or toes, or pitted nails, tell your provider; treating early can protect your joints.

How we treat psoriasis at Glow Theory

We cannot change your genes, but we can calm the immune activity in the skin and help you manage your triggers. Depending on the type of psoriasis and how much skin is involved, your plan may include:

• Prescription topicals, such as steroid and vitamin D creams
• Intralesional injections for a few stubborn, thick plaques
• Light therapy and coal tar products for wider areas
• Referral for biologics for moderate to severe psoriasis, through dermatologists we trust

Day-to-day care makes a real difference, especially in winter; see our winter psoriasis skincare guide and is natural sunlight good for psoriasis? If you have brown or Black skin, our guide to psoriasis in skin of color explains why it is often missed.

Medical dermatology visits at Glow Theory are $150 – $375. See our psoriasis treatment in Carlsbad page or book a visit at our studio on El Camino Real.