Yes, it is – at least in part - a biochemical matter. Mosquitoes and ticks are attracted to ammonia, carbon dioxide, and fatty acids. But there are numerous other chemicals emitted by humans and animals, e.g. hexanal, 2- heptenal, nonanal, furfural, benzaldehyde, and 2-hydroxybenzaldehyde, heptanal, 2-, 3-, and 4-methylbenzaldehyde, 2-nitrophenol, 4-methyl-2- nitrophenol, gamma-valerolactone, and many more. All named above can be detected by ticks (and mosquitoes) and influence its behavior.
Now add perfumes, hair spray, soaps, washing detergents, deodorants, repellents, …. Everything that causes us to smell differently can cause different attraction to mosquitoes and ticks.
Therefore it can not be easily predicted who gets most bites. It is not "the more you have the more often you get bitten", instead certain combinations of these chemicals seem to be viewed as "very delicious" by some mosquitoes and ticks.
The attractivity of a person for these blood suckers depends on age, sex, if a female then also what time of the monthly cycle, and on the bacterial flora you have on the skin. All these factors influence which and how many chemicals you emit.
In addition being bitten by a tick it is also depended on physical properties, mainly: size, color, movements, body temperature, and humidity in the exhaled breath. Even the best smelling object will never be bitten if it does not have around 37 degree Celsius.
And finally the number of bites depends on behavioral factors. A person that slowly walks along a path but never leaves it and never stops gets much less bites than one who leaves the path two or three times to observe something, stopping for several seconds or minutes, especially if lots of leafs and grass are around – favorite spots for ticks to wait for a host.
What can be done against being bitten? Wear long sleeved clothes, show little bare skin. Use repellents. Avoid being outside at dawn - go for your walk in the morning. Be careful with perfumes; some really attract insects and ticks. Have a shower before you start. This reduces body odors and keeps attraction fo arthropods to a minimun.(Works well up to two hours.)