Singulair has less side effect than oral steroids. If adding Singulair means using less steroid and having less asthma attacks. I think it's a good thing. Oral steroids should be avoided unless he has severe asthma.
Xopenex is an isomer of albuterol. However, Xopenex has less palpitation side effect than albuterol. My ds has xopenex, but his hands still shake after the treatment.
In general, inhaled steroid + albuterol or xopenex (Short acting beta agonist) are the main treatment for asthma. It's important to have both. After that, the doctor should add Singulair or a long acting beta agonist like serevent if age appropriate. Cromolyn can also be added on. Oral steroid is the last resort.
Singulair gave my ds a 24 hour fever. I remember seeing his fever came on about an hour after taking Singulair and the fever was gone exactly 24 hours later. Nothing is said on the drug information of Singulair about nightmares. However, it does cause <1% of agitation, insomnia and a whole list of things. All drugs have side effects. It depends on whether the side effects shows up on you or not.
If pollen is an issue, does he have allergy medications, like Allegra and a nasal spray?
