Hands and arms are swollen, i noticed it yesterday. what could be the cause?

It depends: Sometime these swelling are are positional due to gravity. Other-time, could be due to insect bite or allergies, could be anything.

Edema: Is there associated redness, pain or itching. If not it could be from the arms having been in a dependent position for a lengthy time such as on a prolonged walk. Some people get swelling of hands and feet from exercise. This is different from angioedema which is an allergic reaction. See your physician if swelling persists or worsens.

Swelling: Could be edema, or arthritis with swelling due to inflammation as two possibilities. Real diagnosis will come form an examination, best wishes.

Reaction to drug?: Two things can cause hands and arms to swell without swelling of your legs or abdomen. The first is blockage of the large veins in the chest that drain the blood from the arms. I can't think of any problem that will do this in a 29 year old. The second is a response to a cream that you put on your arms. If not and it persists you need to see your doctor this week.

Allergies???: Impossible to know without a history and exam. Food allergies, a bug bite, other alleriges, etc. See a dr. And/or possibly an allergist is the problem persisits.

Swelling: It could be many things. Could be related to heart or kidneys or liver.

Many things: It is very hard to say without more history. Swelling can be from an allergic reaction to something you came in contact with or to a food, medication, etc. If associated with joint pain it could be related to an arthritis. It could be normal from exertion or even heat. Some medical conditions can result in swelling. If it continues or worsens get a history and exam done to help make a diagnosis.