Mono (also known as kissing disease) usually is caused by the Epstein-Barr virus (EBV). It is most often seen in teens and young adults. Children can get the virus, but it often goes unnoticed because their symptoms are mild. Older adults usually don't get mono, because they have better immunity to the virus.  Mononucleosis is contagious and can cause the following complications:

• Anemia — a decrease in red blood cells and in hemoglobin, an iron-rich protein in red blood cells
• Thrombocytopenia — low count of platelets, which are blood cells involved in clotting
• Heart problems — an inflammation of the heart muscle (myocarditis)
• Complications involving the nervous system — meningitis, encephalitis and Guillain-Barre, syndrome swollen tonsils — which can block breathing. 
• Mono can cause the spleen to swell. Severe pain in the upper left part of your belly may mean that your spleen has burst.
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• Caution: Monocine may cause a sharp sting for a few seconds.  This sharp harp sting is due to phenolic monoterpene Carvacrol phenol property, an isomeric with thymol is a major component of the essential oils of plants of the Labiatae family used in Monocine including Origanum vulgare and Thymus.   Monocine may also help MRSA (Methicillin-resistant Staphylococcus aureus)  a bacterium that causes infections in different parts of the body.