In this randomized double blind cross-over study 8 healthy persons were injected with 0.8 ng/kg body weight lipopolysaccharide (LPS) /endotoxin and placebo at two different occasions. The aim was to investigate how pain sensitivity and health perception change in response to an acute immune activation.

Eight healthy participants were included in this randomized and balanced double blind cross-over study. They were injected two times, once with the active component and once with placebo. Participants were recruited by advertising and screened through questionnaires and a health examination by a physician. They were asked not to engage in strenuous physical activities, sleep regular hours and refrain from alcohol the day before the experiment. If the participants felt ill, e.g. coming down with a cold, they were instructed to call and were rescheduled for a later appointment. C-reactive protein (CRP) was assessed to exclude participants having an ongoing infection on the experimental day. Pregnancy was also an exclusion criteria and a pregnancy test was administered for all female participants on arrival. Several pain sensitivity measures were performed baseline and at peak inflammatory response 1-2 hours after injection. Subjects filled out questionnaires at baseline, 90 minutes and 4,5 hours after injection.

The study and the procedures used in the study are described in detail here: https://openarchive.ki.se/xmlui/bitstream/handle/10616/44650/Thesis\_Bianka\_Karshikoff.pdf?sequence=8\&isAllowed=y

The following papers have been published using data from this study:

Olsson MJ, Lundstrom JN, Kimball BA, Gordon AR, Karshikoff B, Hosseini N, Sorjonen K, Olgart Hoglund C, Solares C, Soop A, Axelsson J & Lekander M. The Scent of Disease: Human Body Odor Contains an Early Chemosensory Cue of Sickness. Psychol Sci. 2014 Jan 22.

Sundelin T, Karshikoff B, Axelsson E, Hoglund CO, Lekander M, Axelsson J. Sick man walking: Perception of health status from body motion. Brain Behav Immun. 2015;48:53-6.

Karshikoff B, Lekander M, Soop A, Lindstedt F, Ingvar M Kosek E, Olgart Höglund C, & Axelsson J. Modality and sex differences in pain sensitivity during human endotoxemia. Brain, Behavior, and Immunity. 2015 May;46:35-43

Inclusion Criteria:

• Healthy subjects

Exclusion Criteria:

• Diagnosed physiological or psychiatric disease
• Needle anxiety or blood phobia
• Regular medication (excluding contraceptive pill)
• Infection in the last two weeks
• Pregnancy or breastfeeding
• Smoking
• Excessive alcohol use
• Body mass index in the range of obesity (>30 kg/m2) or underweight (<18.5 kg/m2)
• Invisible veins in the antecubital area of the arms