"A Contraindication is a condition or something that makes massage not recommended because massage can make something worse. Blood clots are one example of a contraindication for massage."
Many people want a massage to feel better, and there are many things that massage can help with. However there are occasionally conditions or issues that, if a massage was received, would make the condition worse and those conditions are known as "Contraindications". Massage manipulates the muscles and tissues on the body, and also has a strong effect on circulation and how blood, lymph, and more flows through the body, so if there are things floating around that the body shouldn't be spread, massage is contraindicated for that person. Likewise, if a condition exists that may harm the massage therapist, that is also considered a contraindication.
Just a few contraindications include:
Blood clots - we don't want circulation dragging them into the heart, lungs, or brain
Open wounds/sores - if something is healing, we don't want to rip off the scabs and start bleeding
Shingles - This puts the therapist at risk if the sores are open, they can be exposed, plus open sores - see above
Pitting Edema - if swelling or edema is so bad that it leaves a mark, something else is going on in the body, possibly in the kidneys, and we don't want to overtax any organs
Bruises (severe) - some small ones are ok to work over lightly, but a severe contusion that is still black and purple is actively healing, so we let it heal
Fever/contagious diseases/illness - while a massage may feel good if you have body aches, the body needs to heal, and massage can put more strain on your system so your body needs to rest, plus an infectious disease puts the therapist at risk
Hypertension/uncontrolled high blood pressure - massage over time can ultimately lower blood pressure, but it can temporarily raise it, so we want to make sure it isn't too high to start with.
Some contraindications completely forbid massage at all, while other such as bruises can be worked around or the body part where the bruise appears can be avoided. If you have any questions about if a condition is contraindicated, ask both your doctor and therapist - sometimes doctors will say "this conditions needs you to relax" and you think "cool, get a massage" but that isn't always the best idea. Specifically ask the doctor if massage is ok, and fully disclose any conditions to the therapist as well so they know what they are working with, and nay precautions they need to take to not make a condition worse.