Apples do not cause constipation. WebMD reports that apples often help treat constipation rahter than causing it. The only known side effects of apples come from apple seeds, which contain small amounts of cyanide, and could be fatal if too many are ingested.
According to the Children's Hospital of Wisconsin, apples may help soften stool, which can be used to treat constipation. Symptoms of constipation include a decrease in bowel movements, hard and dry bowel movements, or movements that are painful or difficult. Poor dietary choices, lack of exercise, emotional issues, intestinal abnormalities, endocrine or nervous system issues, or medications are catalysts that sometimes factor into constipation.