What causes a purple/deep blue color in the arms of a five month old?

I have never heard of that and if I were the mother I would take baby in. If you think you could convince her to get it checked then I would.

I would be concerned that blood wasn't flowing right in the arms.

A bluish color is generally a sign of poor circulation....she needs to have that baby checked out.

My child did that when she was a baby and she stoped breathing.She was diagnosed with a heart condition that caused her to be like that.The heart condition caused restricted oxygen and poor circulation.That baby can die!If you can not convience her to take the baby to the hospital you need to call the police or CPS because that is child abuse when you do not get a child medical care.I know she is your friend but if you do nothing and the baby dies it is not just going to be her fault it will also be yours if you know something is wrong but do nothing and in some states if you know that a child is being abused and do not report it you will get in trouble as well.And with the way that you are describing the baby's arms,it is common sense that something is wrong and that the baby needs help now.The baby can not take its self to the hospital or ask for help.Please do the right thing and let me know what happens.

well in my youngest childs short, almost 4 month, life, ive experienced blue legs, and blue arms AND legs. i have a three year old also and had NEVER experienced this before, and i FLIPPED! come to find out the blue legs were from a onsie that was too tight, and i had no idea. i unsnapped it in the middle of a fast food joint and all was well. the blue arms and legs happened this weekend, and it turned out he was just really cold, but wasnt fussing or anything so i had no idea, because he had a sleeper on and his hands were the last thing to change color. as soon as i saw his hands i undressed him to look everywhere else and i guess my hands were cold too cuz i didnt even notice, but assumed thats what was wrong. i asked my mom to turn up her heat (cuz thats where we were at the time) and i put two outfits on him, and he was fine. if he/shes not cold, and not wearing small clothes, id take him/her to the ER.

yeah to pps, that kid needs medical attention now!!!!!!!!!!!!!!

I'd be very concerned. Like the others here, my first thought is poor circulation with can have any number of causes from blood clots, to heart problems or something simple like clothing too tight or cold hands. I put my duaghter in the bath and her hands and feet turned blue. It was becuase she was really cold and the warm water reacted with it some how. As she warmed up, the color went away. But if it's a constant color and not going away, I'd be concerned.

TAKE THAT BABY TO THE EMERGENCY ROOM!!!! DON'T WAIT ANY LONGER. COULD BE A SERIOUS HEALTH PROBLEM. HOPE YOUR FRIEND'S BABY WILL BE OKAY. GL.

I agree heart problem.

Poor circulation. She needs to be checked for a heart problem.