Watch a video on hay fever.
Marlon, 33, is one of Britain's most successful sportsmen. He was part of Britain’s Olympic gold medal-winning relay team at Athens in 2004 and has received an MBE for his contribution to British sport.
To get there, Marlon has had to overcome numerous sporting injuries, including a hamstring injury in 2000 that stopped him from competing in the Sydney Olympics that year. But what many people don't know is that he's also had to learn to manage severe hay fever.
"It’s something I've had to deal with since childhood," says Marlon. "It runs in the family."
Nearly 15 million people in the UK have hay fever. Like most of them, Marlon expects his seasonal bouts of sniffing and sneezing. Unlike most people, he has gold medals resting on his physical condition, especially in the summer racing season.
"I get the usual symptoms of itchy eyes, nose and throat, but I also get exercise-induced asthma. Because I'm so allergic to the pollen in the air, it causes my chest to tighten when I run. So if I don’t manage my hay fever carefully, it can seriously affect my performance on the track.
"I have to get clearance every year from the IAAF (International Association of Athletics Federations) so that while I'm competing I can use an inhaler to control my asthma. My hay fever is at its worst at the height of summer when there is more pollen in the air and this is when I have to be most vigilant with my medication.
“I don’t have to be so careful in the winter months when I'm not competing, but I still have to monitor the condition closely."
Eating well'I used to suffer badly when I was younger but it never stopped my love of sport'
Despite living with hay fever since childhood, Marlon has never let it hold him back from his active lifestyle.
"I used to suffer badly when I was younger because I'd rub my eyes until they were red raw, but it never stopped my love of sport. When I was at school I used to get involved in everything I could.
"My favourite sports were basketball and football which, unfortunately, I don’t really have time to play now because my training schedule is so hectic."
As an Olympic athlete, Marlon trains six days a week to stay at the peak of his physical and technical fitness. He also keeps a close watch on his diet.
"It's so important that I eat well when training. As a sprinter, protein is a vital part of my diet because when you sprint you tear your muscles on a microscopic level. You then need to replenish the protein in your system for muscle building. So I eat lots of meat for protein and carbs for energy."
Keeping in shapeMarlon has always kept a close eye on his health and fitness. "My mum's a nurse, so from a young age I was made very aware of my health. Apart from hay fever, the other problem that runs in the family is high blood pressure. My gran has it. She's had to control her diet and cut down on saturated fat and salt.
"I'm aware this is something I may have to watch out for when I get older. For the moment, though, I'm concentrating on keeping in shape and aiming to compete in the Beijing Olympics."
Marlon thinks the 2012 Olympics will have a positive effect on the UK's health. "I hope it will act as a catalyst to improve our lifestyles. I don’t think they're particularly great in the UK. You only have to turn on the TV to see the programmes about our unhealthy lifestyles, from booze culture to obesity.
“After the event is over we'll be left with some great sporting facilities, which will hopefully inspire kids and adults alike to keep themselves healthy."