Overview of Phototherapy
Phototherapy is a key treatment method used in the field of dermatology which has significantly changed how various skin diseases are managed. Specifically, this therapy involves intentionally exposing the skin to non-harmful types of radiation, commonly from the ultraviolet (UV) portion of the electromagnetic spectrum.
Phototherapy often uses ultraviolet A (UVA), ultraviolet A-1 (UVA-1), a combination of UVA and a photosensitizing drug called psoralene (PUVA), and ultraviolet B (UVB). The UVA spectrum usually sits between 320 and 400 nanometers in wavelength, UVA-1 being the longer wavelengths among them (340-400nm). The UVB spectrum, on the other hand, is found between 280-320nm, and is commonly used in two forms – broad-band (BB-UVB), which also includes shorter wavelengths from the UVA spectrum, and narrow-band (NB-UVB), which utilizes specific wavelengths between 311 and 313nm.
There are a few specialized types of phototherapy available, including lasers, photodynamic therapy, bath-PUVA, and extracorporeal photochemotherapy. Even so, phototherapy still remains the go-to treatment approach for various skin conditions such as parapsoriasis, psoriasis, eczema, atopic dermatitis, vitiligo, and other skin disorders.
Different properties associated with UVB phototherapy include anti-inflammatory, immunosuppressive, and cytotoxic effects – although the exact processes through which these effects take place remain unclear. It’s hypothesized that various cellular and immune activities are induced or altered by this therapy, leading to the death of certain types of cells, like T lymphocytes and keratinocytes, which help the body fight diseases. Similarly, PUVA is thought to work by altering the structure of DNA, preventing it from copying itself, depleting immune cells in the skin, and suppressing the function and movement of T-lymphocytes – a type of white blood cell. Meanwhile, UVA-1 phototherapy impacts tissues deeper within the skin, triggering specific proteins and signals that help soften hardened skin. Photopheresis, a process related to phototherapy, can have the effect of making specific immune responses more effective without weakening the entire immune system.
Why do People Need Phototherapy
Psoriasis is a skin condition that causes red, flaky, and itchy patches of skin. Narrow-band UVB light therapy is often used to treat this, except for in cases of severe, widespread psoriasis, where PUVA (a combination of a drug and ultraviolet light) can be used. UVB light therapy is safer for pregnant women and can be combined with some skin creams. PUVA can be considered for patients whose skin doesn’t improve after UVB treatment or for those who experience a relapse soon after treatment.
For chronic eczema, another skin condition that causes itchy, inflamed, cracked skin, light therapy can also be very helpful. UVB light therapy is usually the first treatment option for widespread eczema, while topical PUVA therapy is a first-line treatment for localized eczema affecting the hands and feet.
Mycosis Fungoides, a type of skin cancer, can be treated using both UVB light therapy and PUVA. UVB light therapy is helpful in early stages of the disease, while PUVA is more effective for later stages. PUVA can also be combined with other treatments for advanced cases.
Light therapy is also used for treatment of vitiligo, a condition that causes white patches on the skin due to loss of pigment. In cases where topical treatments (creams or ointments) are not effective, light therapy can be the next option. However, the relapse rates in vitiligo is quite high, meaning the white patches often come back after treatment.
For Polymorphic Light Eruption, a common skin rash triggered by sunlight, both UVB and PUVA are effective for reducing sensitivity, but UVB is used more frequently due to fewer side effects.
Graft-versus-host disease, a complication that can occur after a stem cell or bone marrow transplant, responds to both oral and bath PUVA as well as UVB light therapy. These treatments can be used as an alternative to steroid treatment.
Patients with Generalized Lichen Planus, a condition that causes purplish, itchy, flat bumps on the skin, who do not respond to immune-system suppressing medications can use light therapy as an alternative treatment.
Other conditions that can be treated with light therapy include pityriasis lichenoides chronica (a rare skin disease causing red, scaly spots), granuloma annulare (a skin condition causing red or purple bumps), mastocytosis (a disease causing too many mast cells in the body), chronic spontaneous urticaria (a type of hives), and generalized pruritus (itchy skin).
When a Person Should Avoid Phototherapy
There are certain conditions in which it is not suitable to perform a specific type of skin treatment. These include the following situations:
When a person has a condition that could make the treatment risky or ineffective. For example, conditions such as Dysplastic naevus syndrome (a disorder characterized by many unusual moles), Systemic lupus erythematosus (an autoimmune disease where the body’s immune system attacks its own tissues), Dermatomyositis (a rare inflammatory disease that causes muscle weakness and skin rash), and genetics-related skin cancer syndromes like xeroderma pigmentosum or Gorlin syndrome.
Other less known conditions like Bloom syndrome and Cockayne syndrome, which are genetic disorders, also make the skin treatment unsuitable. If a person is unwilling or unable to follow safety procedures, or if they have serious health problems (like severe heart or lung disease) that make it unsafe for them to stand, then this skin treatment wouldn’t be advisable.
There are also some situations where the treatment can still be done but requires close monitoring or careful consideration. These include: individuals who have been exposed to arsenic or harmful radiation, those with a history of melanoma (a type of skin cancer), pregnant women, and those with skin conditions that could turn into cancer.
It might also not be advisable for people who are on medication that weakens their immune system, those with a condition called photo-induced epilepsy (a type of epilepsy triggered by flashing lights), individuals with cataracts (clouding of the lens in the eye), or people with skin disorders like Bullous pemphigoid/pemphigus (rare skin conditions that cause blisters).
People with significant liver problems, non-melanoma skin cancer, or anyone under the age of 16 should also consider these risks carefully.
Equipment used for Phototherapy
Phototherapy, a treatment method that uses light, uses varied equipment to focus the treatment on the appropriate areas of the body. This can involve whole body cabins, small panel devices, large panel units, and narrowband UVB point sources, each serving a unique purpose.
Whole-body cabins are large equipment with long tubes that emit light, lining the walls, and facing reflective metal surfaces. This setup allows for an evenly distributed and efficient treatment. On the other hand, small panel devices are typically used for treatment of palms and soles.
Point source devices, another type of equipment, are designed to focus the treatment on affected areas of skin, while avoiding healthy areas. However, when using this method, careful attention is needed to avoid applying too little or too much treatment to areas where the treatment beams overlap.
‘Calibration’ and ‘dosimetry’ are two crucial aspects of phototherapy. These terms describe the process of calculating the dose and measuring the treatment effect, respectively. They are crucial for adjusting the treatment intensity to each patient’s needs. For instance, a term called ‘designated patient irradiance (DPI)’ is used. DPI is the average intensity of light in a whole body cabinet that a patient will be exposed to during therapy. This intensity is measured at 12 different body positions to ensure an even distribution of light over the entire body.
Preparing for Phototherapy
Before starting light therapy or phototherapy, there are some safety measures to take. This process includes regular checks on the equipment and certain precautions to keep you safe. Before you step into the booth where the treatment happens, you should put on safety goggles, cover your genital area, and wear a face shield. To make sure we apply the right amount of light to your skin, we conduct tests to figure out the smallest amount that will still be effective, without causing skin redness or a similar reaction. We also keep a record of the light intensity coming from the booth, using a special tool called a radiometer.
Regular cleaning and inspection of the booth and light bulbs is also a part of the process, and the bulbs are replaced whenever necessary. Once your light therapy session is over, you should continue to wear sunglasses that block ultraviolet (UV) light until the sun goes down. To further protect your skin from the sunlight, make sure to regularly apply sunblock on parts of your skin exposed to the sun.
How is Phototherapy performed
The sun’s electromagnetic spectrum includes three types of ultraviolet (UV) rays: UVA (320-400nm), UVB (280 to 320nm), and UVC (less than 280nm). This spectrum is the range of light and radiation between X-rays and visible light. UV radiation (UVR) can also be created artificially using a special technique. This involves the use of fluorescent tubes filled with mercury vapors and coated with phosphorus.
Here’s how this works: an electric current passes through the tubes, exciting the mercury electrons. These excited electrons are absorbed by the phosphorus coating and then, through a process called fluorescence, they re-emit radiations with longer wavelengths. By altering the phosphorus, we can produce UVA and UVB rays.
It’s important to note that UVA rays are capable of penetrating deeper than UVB rays. However, UVB rays are more easily absorbed by DNA, the genetic material in our cells, than UVA rays. Understanding this process helps us comprehend how UV radiation affects us and how we can protect ourselves.
Possible Complications of Phototherapy
UVB therapy, which uses ultraviolet light to treat certain skin conditions, can sometimes cause complications. Just after treatment, some people might experience redness, burning, pain, swelling, and blister formation, especially those with fair skin, those carrying extra weight, or those taking certain medications. In some cases, UVB therapy can cause a flare-up of cold sores. If redness is mild, you can usually use soothing creams and corticosteroid creams. A rare side effect is the formation of blisters on areas of skin affected by conditions like psoriasis, but this is usually not painful.
Long-term or repeated UVB therapy can cause changes to the skin such as a leathery appearance, dryness, wrinkles, changes in color, loss of elasticity, and increased fragility. There is some evidence to suggest UVB therapy may be linked to cancer, but this risk is not fully understood. A certain type of UVB therapy, called narrow-band UVB (NB-UVB), appears to carry less cancer risk than other types. Protective covering of sensitive areas is generally advisable during these treatments.
Complications can also occur with PUVA (psoralen and ultraviolet A) treatments. Just after treatment, some may experience anything from mild redness to severe discomfort including swelling, blistering, and a general feeling of being unwell, including fever. Nail damage, such as separation from the nail bed or bleeding under the nail, is less common. Some people might feel nauseous, especially those taking the medication 8-MOP by mouth; taking anti-nausea medications or adjusting the intake of psoralen medicine can often help with this. Like UVB, PUVA can also reactivate cold sores.
With long-term use, PUVA can create multiple rough patches on the skin in areas not normally exposed to the sun, for example, the legs, trunk, and sides of the hands, feet, and digits. There is strong evidence to suggest PUVA therapy carries a cancer risk, particularly for a type of skin cancer called squamous cell carcinoma, and the risk increases with the dose. Additionally, PUVA can stimulate the growth of other skin cancers like melanoma and is thought to possibly increase the risk of internal cancers, particularly of the lymph system. There is some evidence to suggest psoralen, a component of PUVA therapy, can penetrate the lens of the eye and has been detected in some humans. As a result, there has been concern about possible cataract development, particularly in those with pre-existing eye conditions or in children and people with skin conditions like atopic eczema. It is therefore advised these individuals wear protective eyewear during PUVA treatment.
What Else Should I Know About Phototherapy?
Phototherapy, or light therapy, is a simple, safe, and effective way to treat various skin conditions. It’s also affordable and tends to have fewer side effects than some other treatments. Skin diseases can impact everyday life significantly, and phototherapy offers a powerful solution compared to creams or medications taken by mouth.
The procedure is especially effective in treating a range of skin conditions including psoriasis (a condition that causes skin to build up forming scales and dry patches), mycosis fungicides (a type of lymphoma which affects the skin), atopic dermatitis (a common type of eczema that causes the skin to become itchy, red and cracked), pityriasis Versicolor (a common fungal infection that causes small patches of your skin to become scaly and discolored), chronic urticaria (a skin condition where red, itchy hives persist for six weeks or more), palmoplantar pustulosis (a chronic skin condition causing pustules on the palms of the hands and soles of the feet), and vitiligo (a long term condition where the skin loses its pigment color).
One of the significant benefits of phototherapy is that it helps avoid the side effects that come with taking medications through the mouth because it is a safer substitute.
