In sickle cell disease (SCD), polymerisation of haemoglobin S and the resulting shape change of the red blood cells (RBC) lead to vascular occlusion and severe painful crises. Permanent inflammatory state and abnormal RBC adhesion to the endothelium trigger these phenomenon. Hydroxyurea (HU) is the only drug that has been shown to reduce clinical severity of SCD, and this was initially attributed to the stimulation of foetal haemoglobin (HbF). However, the clinical response does not correlate consistently with the degree and time of HbF increment, suggesting that HU clinical benefits may involve other mechanisms such as the induction of natural anti-inflammatory response via the hypothalami-pituitary-adrenal axis.