No, Nigrifix Cream should not be used on a 6-year-old child unless it has been specifically prescribed by a paediatrician or paediatric dermatologist. Although it is designed to treat dark, thickened skin caused by acanthosis nigricans, it contains active ingredients such as retinol, lactic acid and urea. These ingredients can be too strong for a child's delicate skin and may cause redness, irritation, peeling or dryness. In addition, dark patches in children may sometimes be linked to underlying conditions such as insulin resistance, obesity, or hormonal problems, so it is important to identify the cause before starting treatment. Until your child is examined by a doctor, it is safer to use a gentle moisturiser and avoid harsh scrubbing of the affected areas. If the dark patches are spreading, becoming painful, or changing quickly, seek medical advice promptly.