UV and Systemics 

Many people with psoriasis find that their skin is clearer in the Summer, when there is more daylight and they spend more time out in the sun, and worse in the Winter, when it is darker.

Even though the sun may help your psoriasis, it is still important to stay safe in the sun and use a high factor sunscreen. The sun may help your psoriasis, but it’ll definitely get worse if you get sunburnt.

UV light therapy is one of the first treatments that may be prescribed by a Dermatologist, and might be used on its own or in conjunction with other topicals, tablets or injections.

The treatment will be given in a phototherapy centre at a hospital, and will usually involve you having to attend two or three times a week for anywhere between four and eight weeks, depending on the kind of light therapy you are receiving.

It is important to remember that, during UV light therapy, the Dermatology team are closely controlling and monitoring your exposure to UV. If you use sunbeds outside of the hospital, it can make it difficult to ensure your exposure stays within recommended limits. As with being out in the sun, or using sunbeds, exposure to UV rays through UV light therapy can increase the risk of developing skin cancer.

The UV therapy you receive from a Dermatologist is different to that of a sunbed. The UV light used to treat psoriasis is very specific and the machines are maintained regularly to ensure the correct dose is given.

UVB Therapy

UVB treatment involves exposing the patient to a very narrow band of UVB wave. This interferes with the behavior of chemicals in the body, leading to a slowing-down of the very fast skin cell turnover that occurs in psoriasis. During the treatment, you will stand in a UVB cabinet for a period of a few seconds, up to several minutes.


PUVA uses a combination of UVA light and a tablet or cream called Psoralen to treat psoriasis.

UVA light works in a similar way to UVB, but it can also reach other cells in other, deeper layers of the skin. Because of this, PUVA can sometimes be more successful on thicker or more stubborn plaques of psoriasis than UVB.

The Psoralen is used to make the skin more sensitive to UVA light, and you will either take it as a tablet two hours before light treatment, or apply it as a cream to your skin around half an hour before.

If you take the tablet form of Psoralen, you will need to wear UVA-blocking protective glasses for between 12 and 24 hours after treatment. This is because the tablet will also make eyes more sensitive to UVA, which could cause the formation of cataracts. These glasses need to be worn anywhere the sun shines, and bear in mind that UVA rays penetrate through glass.

Like UVB therapy, you will stand in a phototherapy cabinet for a period of a few seconds, up to several minutes. There are also hand and foot PUVA machines to treat psoriasis just in these places, and avoid exposing the whole body.


‘Systemic’ medicines are medicines that affect the whole body (or ‘system’), rather than just targeting one area.

They are prescribed by a Dermatologist, and a patient usually has to have tried a number of topical treatments and light therapy without much success, or have quite a lot of psoriasis, before getting a systemic treatment.

Systemics usually come as a tablet or liquid that you swallow, anywhere from daily doses to once a week. Your Dermatologist will tell you how much to take and how often. It can be a few weeks before you start to see an improvement in your skin, so, as with other psoriasis treatments, it’s important to keep taking it in the way you’re told. Systemics can be prescribed as monotherapy (just them on their own), or in combination with topical treatments, UV Light Therapy, or a biologic treatment. The systemics most commonly prescribed for psoriasis include methotrexate, acitretin and ciclosporin.

Systemics are serious treatments, which is why they aren’t dished out to everyone with a bit of psoriasis. The effect that some of them have on your immune system means that you may be more prone to infections, and will need to have yearly flu jabs and be regularly monitored and tested for infections such as TB.

The list of possible side effects can be scary and offputting, but it’s worth remembering a few points:

  • They are possible side effects, you may not experience them. The manufacturers have to put every side effect that more than a certain number of people have reported on the list. Many of the side effects on the list may have only been reported by a very small number of people. You may not experience any side effects at all, and it could be that any you do get are mild, or manageable by changing your dose.
  • Your Dermatologist is aware of the risks of these treatments, and you will be very carefully monitored. Liver and kidney function tests are often carried out (via simple blood tests), as are tests to look for infections and monitor blood pressure. This means that if a problem arises, the Dermatologist can deal with it quickly.
  • Many people get very good results from systemic treatments; the best effect is the possible clearing of your psoriasis!

Do make sure that you talk to your Dermatologist or Dermatology Nurse about any concerns you may have about your treatments.

For further information about psoriasis, or for a list of resources used in the production of this information resource, please contact the Psoriasis Association. December 2017 (Review: Dec 2020).

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