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In the treatment of vitiligo, particularly when dealing with white patches next to the nose, determining the appropriate light dose for phototherapy is crucial. This decision must be based on a variety of factors, including the location of the lesion, the patient's age, the severity of the disease, and their skin sensitivity to light.

Factors Affecting Light Dose Determination

The initial dose of phototherapy for vitiligo is often determined based on the Minimal Erythema Dose (MED), which represents the minimum amount of light exposure required to produce a visible redness in the skin. This MED value varies among individuals and can be determined through a photosensitivity test conducted at a hospital. For the nose area, which is relatively sensitive, the initial dose should generally be set conservatively.

• Location of the Lesion: The nose and surrounding areas are typically more sensitive to light than other parts of the body. Therefore, a lower initial dose is recommended, typically around 200 mJ/cm² for facial areas, including the nose.
• Patient Age: Children generally require a lower initial dose than adults due to their more sensitive skin. For children, the initial dose for facial areas, including the nose, might be as low as 100-150 mJ/cm².
• Disease Severity: The severity of the vitiligo also influences the choice of initial dose. In milder cases, a lower dose may suffice, while more advanced cases might require a slightly higher starting dose.
• Skin Sensitivity: The MED value, which is specific to each individual, plays a significant role in determining the initial dose. A photosensitivity test can provide this crucial data.

Adjusting Light Dose Based on Response

The initial dose is just the starting point. The actual dose administered during subsequent sessions should be adjusted based on the skin's response to the previous session. Here are some guidelines:

• No Response: If there is no visible redness or other reaction after the initial phototherapy session, the dose can be increased by 10-20% for the next session.
• Mild Redness: If mild redness appears and disappears within 24-48 hours, the current dose is considered appropriate and should be maintained for several sessions.
• Excessive Redness: If there is excessive redness, swelling, or other adverse reactions, the dose should be reduced immediately and the treatment paused until the skin recovers.

Phototherapy Techniques and Equipment

Different phototherapy techniques and equipment may have specific dosage recommendations. For example, 308-nm excimer laser is a commonly used treatment for localized vitiligo, including patches next to the nose. The initial dose for this type of treatment is typically set at 150-300 mJ/cm², depending on the individual's MED value.

It's important to note that the frequency of phototherapy sessions also plays a role in treatment effectiveness. Generally, sessions should be spaced out to allow the skin to recover, with a recommended frequency of 1-3 times per week.

In conclusion, determining the appropriate light dose for phototherapy of white patches next to the nose in vitiligo involves a careful consideration of multiple factors. By starting with a conservative dose and adjusting based on the skin's response, effective and safe treatment can be achieved.