You stand in front of the mirror ''umming'' and ''ahhing'' about what top looks good and what jacket doesn't?

This weekend you don't have to think twice about it: wear something blue.

Fairfield will turn blue on Saturday to raise awareness for people who have PKU.

Phenylketonuria affects 1 in every 10 000 babies born in NSW each year - but not many people know about the condition.

Saturday, May 1 is PKU Awareness Day and Fairfield residents have the chance to wear blue to raise understanding about the condition.

PKU is a genetic disorder which stops the body from be able to break down an amino acid called phenylalanine.

The diet thats sufferers must follow is stricter than those on The Biggest Loser television program.

People with PKU can not eat meat, chicken, fish or dairy and mainly eat fruits, vegetables and low protein pasta and bread made from special flour.

Lucia Tilocca has a three-year-old daughter who has PKU.

She said that many people think PKU is "just a diet''

"As a mother of a 3 year old PKU child living with a restricted diet isn't always easy,'' Ms Tilocca said.

"At aged 3 my daughter has many questions about PKU and although it's hard to explain to her I know she understands in her own way.''

She said fundraising for PKU research and youth activities is difficult because people do not know what the condition is.

"The support of the local community is priceless and appreciated by all PKU families,'' Ms Tilocca said.

"We don't know whether there will ever be a cure for PKU but what I do know is that my daughter has educated many people since her birth and continues to raise the awareness of this rare but restricting condition.''

Show your support for sufferers of PKY by wearing blue this Saturday.

You can also find out more about the condition and donate online at www.pkunsw.org.au.