Inhaled corticosteroids are the most effective medicine to treat persistent asthma. Inhaled corticosteroids are asthma controller medicines. Asthma symptoms happen less often when an inhaled corticosteroid is used every day. When used every day, these medicines make the breathing tubes less sensitive by blocking the inflammation that leads to asthma symptoms.
Using a controller medicine reduces the need for rescue medicines and lowers the chance of needing to go to the emergency room for an asthma attack.
Because the main problem in asthma is long-term inflammation in the lungs, corticosteroids are often used to treat asthma. Corticosteroids help to reduce and prevent the swelling and excess mucus in the airway caused by inflammation.
For most people with asthma, corticosteroids are the single most effective medicine because they break the inflammation cycle and reduce the likelihood of future asthma flare-ups.
Inhaled corticosteroids are not like anabolic steroids. Although they have a similar name, they are very different from the anabolic steroids that are abused by some athletes. Also, it is important to know that concerns about using oral corticosteroids do not apply because inhaled corticosteroids are not absorbed into the body to any large extent .
A small number of individuals experience some local side effects, such as a yeast infection (white spots) of the mouth, tongue or throat and occasional hoarseness. Side effects can be avoided by rinsing the mouth after each treatment and using a spacer with a metered dose inhaler .
The most commonly reported side effects were: oral thrush , nausea , headache , and pain in the pharynx or larynx . More rarely reported side effects (occurring in <1% of patients during the clinical trial) include: tachycardia , palpitations , dry mouth , allergic reaction ( bronchospasm , dermatitis , hives ), pharyngitis , muscle spasms , tremor , dizziness , insomnia , nervousness , and hypertension . Patients experiencing an allergic reaction or increase in difficulty breathing while using this medication should immediately discontinue its use and contact their physician. 
Inhaled corticosteroids are medications used to treat asthma. They are taken by using an inhaler. This medication should be taken consistently so that it decreases inflammation in the airways of your lungs and prevents asthma flare-ups. Inhaled corticosteroids are considered the most effective long term usage medication for control and management of asthma. Depending upon the severity of your asthma, your physician may combine an inhaled corticosteroid with a long-acting beta-2 agonist to treat your condition. Oral and intravenous corticosteroids may be required for acute asthma flare-ups or for severe symptoms.