Accurate assessment of skin pigmentation is essential in dermatology for properly diagnosing and managing a wide range of skin conditions. Traditionally, skin colour has been evaluated through visual inspection or by using classifications like the Fitzpatrick skin type. However, these methods can be subjective, culturally biased, and often are centered around lighter skin tones, which may lead to misdiagnosis or inappropriate treatment for individuals with darker skin.

With advances in technology, non-invasive imaging tools such as colorimetry and multispectral imaging now offer more precise and objective ways to measure skin pigmentation. These methods can help provide consistent and unbiased information about skin tone, benefiting both clinical care and research. Despite these technological advances, there is currently no agreed-upon standard for how to measure skin pigmentation objectively in everyday clinical practice or research settings.

This study aims to explore better, more accurate ways to measure skin pigmentation using modern, non-invasive imaging technologies. Traditional methods for assessing skin colour, like visual inspection or classifying by ethnicity, are often unreliable and biased. In this study, researchers will use tools such as colorimetry and multispectral imaging to measure skin pigmentation more objectively.

The study includes two groups of participants: healthy adults and adults with skin conditions. Researchers will measure a value called the melanin index, which reflects the amount of pigment in the skin, and compare it across different areas of the body and among people with different skin tones and conditions.

The goal is to understand how skin pigmentation varies and to see if these new technologies can help doctors more accurately diagnose and manage skin diseases for people of all skin types.

Inclusion Criteria:-

• Age ≥ 18 years
• Ability to understand oral and written Dutch or English

Exclusion Criteria:

For study cohort #1 (Healthy volunteers):

• Extensive tattoos covering >50% of the total body area
• Recent extensive sun exposure (e.g. sun tanning booth or stay in a tropical country) in the last 3 weeks
• Use of self-tanner products in the last 3 weeks

For study cohort #2 (Patients):

• Extensive tattoos covering >50% of the total body area
• Extensive skin lesions covering >50% of the total body area
• Recent extensive sun exposure (e.g. sun tanning booth or stay in a tropical country) in the last 3 weeks
• Use of self-tanner products in the last 3 weeks

For study cohort #1 (healthy volunteers): adult subjects will be recruited at multiple locations to ensure a diverse study population reflecting the full spectrum of skin colour types. Firstly, volunteers will be recruited using flyers at the campus of Leiden University. Along with that, partners of patients visiting the outpatient dermatology clinic of the LUMC. Lastly, subjects will be asked to partake in the study at public spaces (e.g. museums, festivals) that have given consent for this. Thus, subjects will be recruited in person by researchers at the aforementioned sites, through physical advertisements and digital advertisements.

For study cohort #2 (patients with any skin disease): adult subjects with be recruited at the outpatient dermatology clinic of the LUMC and the affiliated hospitals of the CONNECTED (Clinical Network for Trials in Dermatology) in the Randstad region (e.g., The Hague, Zoetermeer, and Amsterdam).