Kelly Smart could not believe what she was seeing. Her son Oscar had a rash and a fever.
"It felt like every time I was blinking there were more dots appearing down his body," she said.
The 11-month-old, who was scheduled to get his MMR jab next month, had caught measles.
According to the NHS, more than 3.4 million children under 16 have not been vaccinated - and remain at risk of getting the disease.
Ms Smart called 111. Once paramedics arrived they "instantly took us to hospital in the ambulance", she told Sky News.
Once at Birmingham Children's Hospital Oscar was treated in an isolation ward.
He was in a bad way - his temperature had risen to 39.9C and doctors worried he was showing signs of sepsis.
"He just looked awful, his eyes were swollen, his top lip was swollen, he was pale," Ms Smart said.
Regarding the timing of the MMR jab, which is given from the age of one, Ms Smart said it was "very frustrating as a mum" that it "wasn't an option" to get Oscar vaccinated sooner.
She added that parents who choose not to vaccinate their children should consider the impact on wider society.
Oscar is now getting better.
More than 200 cases of measles have been recorded by the UK Health Security Agency (UKHSA) across the Midlands, according to the most recent figures.
The majority are in children under the age of 10.
Because measles spreads so quickly, the UKHSA is describing the outbreak as a national incident, and pop-up vaccination centres are opening up.
In Walsall Liz Cooper, a nurse with 40 years' experience, is inoculating people who have missed the jab.
Asked if she had ever seen a measles outbreak like this, she said: "No, not really. It's a real surprise to see the numbers going up so quickly across the West Midlands."
Victoria Atkins, the health secretary, said she was hoping parents would respond to appeals to get their children vaccinated.
She said: "Please go and talk to your GP and have the vaccination - it is completely safe.
"There are two types of vaccination which can help people who may be worried about pork products.
"We've got a vaccine for people who are worried about that and we've got a vaccine for people who aren't so it is really safe.
"We can absolutely help you get vaccinated to help the whole community."