How to help your child if he is jealous of the newcomer

Children are jealous by nature, the new addition to the family may trigger further this sentiment. How to help them to accept the new arrival?
 The children are able to express their jealousy in many ways and in many situations, but surely this feeling is stronger and more frequently in childhood when it comes the birth of a brother or sister. Why did this happen? Up to that point he was just the main character of the house, put on a pedestal and filled with great attention, suddenly feels put aside and displaced by the new figure arrived.
 The first-born between 2 and 5 years are those that occur most strong reactions of jealousy at the birth of a sibling, they become aggressive and hostile towards him, have bouts of anger and take regressive behaviors such as bed-wetting and want a pacifier, all attitudes ranging seconded.
 We know that jealousy is one of the basic emotions of life and causes fear of losing the attachment figure, identified primarily by his mother, the baby knows that alone is lost, for this reason when the parent goes immediately tends to attract his attention with screams and tears.
 Over time, the child becomes aware that understands and can exist even without the mother, although it is a physical and psychological dependence, it will take a long time before you come to understand that love must be shared with others, as a sister or a brother.
 Some parents when they see the child have certain attitudes of jealousy, trying to stifle such feelings with excessive attention and cuddles, but does not require, the reality must be accepted.
 The presence of the newcomer creates in the child so aggressively, forcing his mother to yell and scream all the time: never make the mistake of scolding or punishing him, you may feel humiliated, better let him go, sooner or later will calm down and understand.