Anaphylaxis is a severe, life-threatening systemic reaction that can affect all ages. Anaphylaxis may be caused by a variety of triggers, among them drugs, insect venoms, foods. The clinical symptoms may peracutely involve multiple target organs including the skin, respiratory, gastrointestinal and cardiovascular system. Each age group may be concerned. As anaphylaxis is potentially life-threatening, the essential underlying mechanisms, the effects of biologically higly active chemical mediators released from mast cells or basophils must be blocked or reversed as early as possible. Treatment guidelines focus on interruption of early pathophysiologic mechanisms. Adrenaline is the drug of choice and plays a pivotal role in treatment - for self-administration by patients or voluntary helpers - as well as treatment by physicians. For rapid delivery intramuscular injection is essential. Subcutaneous injections lead to a delay of adrenaline delivery, thus, can be harmful. Obesity is on a distinct rise in industrialized countries and epidemiology displays, so is allergy. The scope of our study was to measure the thickness of subcutaneous fat tissue in 76 randomly selected adults by ultrasound at the recommended sites for adrenaline (auto)injection. Two brands for autoinjection-pens (Epipen (Alk-abello) and Anapen (Fa. Beckmann)) are available on the market in Austria, Germany and Switzerland. Their needle length is 1.4 and 1.2 mm, respectively. We observed that despite a correct injection with the autoinjector pen a intramuscular injection may not be expected in 22 -30% of patients. We recommend to reconsider injection sites in obese adults and to adapt needle length in autoinjector pens accordingly.