It was instead to raise awareness of a group of diseases that often go misdiagnosed, or undiagnosed altogether.

The gallery - as well as City Beach Function Centre - was one of over 150 landmarks across Australia and New Zealand lit up for International Mastocytosis and Mast Cell Diseases Awareness Day.

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Mast cells are a type of white blood cell and are a normal and important part of the immune system.

However, people with mastocytosis experience a build-up of these cells in their tissues, which can have debilitating effects on their health.

Dapto resident Kristin Sinclair is among them, diagnosed with systemic mastocytosis almost 20 years ago.

"When I was first diagnosed I struggled to find anyone in Australia with the disease. I found support via a US-based support group that had an online message forum," Ms Sinclair said.

"Getting support helped me feel less alone - not only had my life changed, but I had a rare disease that even my doctors knew little about."

Then she, David Mayne and Claire Ellis created the Australian Mastocytosis Society (TAMS), to offer support to patients, families, doctors and researchers.

Mr Mayne wants to increase awareness of this group of diseases - which have no cure and in some cases, can be fatal - among both the general public and medical professionals.

"Because it's so misdiagnosed, a lot of doctors... say that it's in the mind, which is not true," Mr Mayne said.

He himself had to wait 15 years for a diagnosis.

Part of the challenge sufferers face is that the symptoms of their illness mimic many other conditions.

These can include rashes, severe flushing, swelling, airway obstructions, migraines, brain fog, musculoskeletal pain, low blood pressure, gastrointestinal problems, and even anaphylaxis, which is a severe allergic reaction.

Mr Mayne said symptoms could also vary significantly between individuals.

"The most consistent thing about a mast cell disease is its inconsistency," he said.

But Mr Mayne said knowledge and awareness of the disease was improving, especially in the last five years.

"It is becoming better and better, but it's taken a long while," he said.

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Ms Sinclair said this was the third year Wollongong had been lit up purple for International Mastocytosis and Mast Cell Diseases Awareness Day, a day she hoped would boost up patients.

"I am humbled each year that people volunteer their time, businesses and buildings to light up for the mast cell community - for me," she said.

"I confess to crying every time I see my town lit up purple - I feel seen and heard and less alone."

Mr Mayne urged people with suspected mast cell diseases to be patient and understanding, and work with their doctors as they tried to find a diagnosis.

Purple, along with pink, are the colours of TAMS because these are the colours that show up on the histology slides in the diagnosis of a mast cell disease patient.

The organisation also uses the hashtag #SpotOurSpots in reference to the spots on the skin that patients often experience, and it has adopted the quoll, with its spotted coat, as a mascot.

For more information, visit the TAMS website.

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