Aging skin becomes less resistant to infection and other diseases because the number of decrease and are less efficient.

There are specified form or types of cells inside the human system, as they serve for the development and sustaining the overall functions of the human body.As there are immune cells like the macrophages, lymphocytes, neutrofils, and many more which are present for the defense mechanism of the body system. While, there are certain limitations for each of these cell's type, like the cells may out run of all there resources or they may degenerate with time causing great distress inside the body system. Aging skin becomes less resistant to infection and other diseases because the number of macrophages or the immune cells decrease and are less efficient.                                                                                                                            

If the experiment was perfomed more then once and you get the same results

1) clean up you lab area2) dispose of the chemicals as instructed by your teacher3) put everything back where it belongs unless your teacher tells you otherwise4) dispose of gloves5) wash hands with soap and water