The Mystery of Eye Colour

How a Child’s Eye Colour is Determined

A child’s eye colour depends on the traits (genes) inherited from their parents. Each chromosome pair contains one gene from the mother and one from the father. The combination of these genes decides the final eye colour.

• Blue eyes: the child inherits blue-eye genes from both parents.
• Brown eyes: the child inherits brown-eye genes from both parents.
• Mixed genes: eyes often appear brown because brown is dominant, but recessive genes (e.g., blue) can always reappear in the next generation.

Dominant and Recessive Genes

• Brown is dominant and produces more pigment.
• Blue is recessive and requires the child to inherit blue-eye genes from both parents.
• This means a parent’s eye colour doesn’t always determine the child’s – you may carry recessive genes that emerge in your child.

Melanin – The Pigment That Gives Eye Colour

Melanin is the pigment in the iris that determines eye colour:

• High melanin → brown or dark eyes
• Low melanin → blue or green eyes, as the cells reflect light
• The maturity of melanocytes combined with sunlight exposure affects how much melanin is produced.

Newborns have immature melanocytes, which means eye colour can change during the first year.

When Does a Child’s Eye Colour Change?

• Eye colour often starts changing around 5–6 months of age.
• By 8 months, the colour is usually more defined – the so-called true iris pigmentation.
• For some children, eye colour can continue to change up to 2 years of age, and in some cases even up to 6 years.
• Eye colour may also change later in life if gene activity is affected.

Tips for Parents Who Want to Track Development

• Take photos over time to document the changes.
• Remember that variation is completely normal – small changes are not a sign of illness.
• Be patient – it can take months or years before the final colour emerges.