The nature and consequences of infatuation are shown throughout the play. Infatuation is often irrational, causing judgment to be lost and personalities changed.
The first hint of infatuation could be seen from Helena's actions towards Demetrius. Helena's actions towards Demetrius in act 1 scene 1 and act 2 scene 1 could be clearly seen by all. In act 1 scene 1, Lysander says that Helena 'devoutly dotes, dotes in idolatry, upon this spotted and inconstant man (Demetrius)' and also Helena who is obviously not thinking clearly even tells Demetrius of Lysander and Hermia's 'stealth' unto the woods, she thinks that she might be able to win back Demetrius' heart by revealing the plans of the elopement of Hernia and Demetrius. While in act 2 scene 1, Helena's relentless and shameless pursuit of Demetrius and not giving up even when Demetrius told her that he does not love her shows that her infatuation with Demetrius is very strong so much so that she even called herself Demetrius' dog- 'I am your spaniel'.
We see that her infatuation with Demetrius makes her do and say things that are irrational and unreasonable. In act 3 scene 2, we can also see the consequences of Helena's infatuation with Demetrius. It causes Helena to lose her self-confidence as Demetrius has hurt her and her pride over and again.
In act 3 scene 2 the roles are reversed, both Demetrius and Lysander become childish men who were obsessed with attracting Helena's attention, just like Helena tried to woo and win Demetrius' heart at first. Demetrius and Lysander had changed from young men who are determined and clear of what they want to men of no judgment and rationality, ridiculously vying for Helena's attention. The consequences were exaggerated declarations...