Last week, some 577,000 children in England passed through the school gates for the first time. Many of them were accompanied on their first day by parents wracked with anxiety, some in tears — and that's before many of them have to receive a letter that begins: "Dear parents, I am writing to inform you that we have a confirmed case of hand, foot and mouth disease in school."

With hundreds of pupils and 30 or so children in a class, diseases can spread rapidly in the school environment, from the common cold (expect plenty in the first year) to chicken pox. But among the neverending list of run-of-the-mill sickness — headlice, chickenpox, conjunctivitis, etc — are Victorian-sounding illnesses that can strike terror in the heart of any parent.

Shortly after my daughter began school, the hand, foot and mouth letter appeared in her book bag. None of us had heard of it and of course first thoughts were of foot and mouth, "an infectious disease affecting cloven-hoofed animals". In the space of two months the following year, we received two letters warning of equally draconian-sounding illnesses. Of course, they all sound worse than they are. So, to save you from that moment of panic, here is a guide to those scarily named diseases:

Scarlet fever, an infectious disease caused by streptococcus bacteria, was once deadly but is now easily treatable with antibiotics in the UK. It is most common among children aged between two and eight (around 80% of cases occur in children under 10), with some 2,000-3,000 cases reported in England each year. Symptoms include a sore throat, headache, fever, nausea and vomiting. After 12 to 48 hours a red rash that feels like sandpaper develops, first on the chest and stomach, then on other parts of the body. Also, look out for a white coating on the tongue, which peels a few days later, leaving a "strawberry tongue" — red and swollen-looking. If you suspect your child has scarlet fever, take them to your GP and then inform the school. Your child needs to be kept at home for a minimum of 24 hours after starting the antibiotics.

Threadworms are small, white worms a few millimetres long that live in the human gut and resemble strings of cotton when they come out in your child's poo. They are easily passed from child to child because so many kids are so bad at washing their hands. The female worm lays eggs around the anus, which causes itching, especially at night. The child scratches the itch, eggs get stuck to their fingertips or under their nails and are then transferred to other people, food, toys, etc. When others come into contact with the eggs, if they touch their mouths and swallow the eggs they become infected too. The good news is that it's easily treatable with a quick visit to the chemist's. It is not necessary to stay away from school, but again good to let your child's teacher know so that a letter can be sent out to other parents.

Hand, foot and mouth has nothing to do with foot and mouth disease in animals. A viral disease, it is most common among children under 10 years of age and is passed on in much the same way as a cold – by coughs and sneezes. Symptoms include a rash on the hands and/or feet and ulcers in the mouth. It usually clears up after seven to 10 days and there's no need for time off school.

Slapped cheek syndrome, also known as fifth disease, is a viral infection that leads to a mild illness with flu-like symptoms, plus a reddening of the cheeks which fades and comes back again, hence the name "slapped cheek". It develops with a lace-like rash on the body and arms and legs that recurs after exposure to light and heat. About a quarter of those infected will show no symptoms at all. There's no treatment, it will just go in its own time.

Chances are that as a parent you will come across these illnesses in one way or another. If you're lucky, the letter is the nearest you'll get to them. But, as school nurse Joy Winks says, it is hard to avoid something like chickenpox or any of the other illnesses when it is going around your child's class or school: "The best way to keep your child healthy is to make sure they have a very balanced diet, plenty of sleep, have all their vaccinations up to date and of course have good hand hygiene."

For more information on the most common infectious diseases and the recommended periods for which children should be kept away from school, go to the HPA website